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Léa El Haddad,1 Mainur Khan,1 Rania Soufny,1 David Mummy,2 Bastiaan Driehuys,2 Wissam Mansour,3 Priya S Kishnani,4 Mai K ElMallah1 1Division of Pulmonary and Sleep Medicine, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA; 2Department of Radiology, Duke University Medical Center, Durham, NC, USA; 3Division of Pulmonary and Sleep Medicine, Department of Medicine, Duke University Medical Center, Durham, NC, USA; 4Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USACorrespondence: Mai K ElMallah, Division of Pulmonary and Sleep Medicine, Department of Pediatrics, Duke University Medical Center, Box 2644, Durham, NC, 27710, USA, Tel +1-919-684-3577, Email mai.elmallah@duke.eduAbstract: Pompe disease (PD) is a neuromuscular disorder caused by a deficiency of acid alpha-glucosidase (GAA) – a lysosomal enzyme responsible for hydrolyzing glycogen. GAA deficiency leads to accumulation of glycogen in lysosomes, causing cellular disruption. The severity of PD is directly related to the extent of GAA deficiency – if no or minimal GAA is produced, symptoms are severe and manifest in infancy, known as infantile onset PD (IOPD). If left untreated, infants with IOPD experience muscle hypotonia and cardio-respiratory failure leading to significant morbidity and mortality in the first year of life. In contrast, late-onset PD (LOPD) patients have more GAA activity and present later in life, but also have significant respiratory function decline. Despite FDA-approved enzyme replacement therapy, respiratory insufficiency remains a major cause of morbidity and mortality, emphasizing the importance of early detection and management of respiratory complications. These complications include impaired cough and airway clearance, respiratory muscle weakness, sleep-related breathing issues, and pulmonary infections. This review aims to provide an overview of the respiratory pathology, monitoring, and management of PD patients. In addition, we discuss the impact of novel approaches and therapies on respiratory function in PD.Keywords: Pompe disease, respiratory complications, respiratory monitoring, respiratory therapy

Background: Late-onset Pompe disease (LOPD), a rare autosomal recessive multisystemic disorder, substantially impacts patients' day-to-day activities, outcomes, and health-related quality of life (HRQoL). The PROPEL trial compared cipaglucosidase alfa plus miglustat (cipa+mig) with alglucosidase alfa plus placebo (alg+pbo) in adult patients with LOPD over 52 weeks and showed improved motor and respiratory function in patients switching treatment from standard-of-care enzyme replacement therapy (ERT) to cipa+mig at baseline. This study evaluated the impact of cipa+mig on patient-reported outcomes (PROs), including HRQoL in ERT-experienced patients, using data from PROPEL., Methods: PROs evaluated included the Subject's Global Impression of Change (SGIC), Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function Short Form 20a, PROMIS Fatigue Short Form 8a, Rasch-built Pompe-specific Activity (R-PAct), and European Quality of Life-5 Dimensions 5 Response Levels (EQ-5D-5L). The proportions of responders in the cipa+mig arm and the alg+pbo arm were compared via chi-squared or Fisher's exact test (patient-level responder analysis), and least squares (LS) mean differences were calculated for change from baseline at Week 52 of the PRO measures (group-level analysis)., Results: At Week 52, patient-level SGIC responder and group-level SGIC analyses favored cipa+mig compared with alg+pbo across all SGIC domains (e.g. 90 vs. 59% responders in the cipa+mig vs. the alg+pbo group for SGIC ability to move around; P = 0.0005; and LS mean difference 0.385; P = 0.02). Similarly, PROMIS Physical Function and Fatigue domains numerically favored cipa+mig in both analyses (e.g. 50 vs. 40% responders in the cipa+mig vs. alg+pbo arm for PROMIS Physical Function; P = 0.37; and LS mean difference 3.1; P = 0.11). R-PAct for both treatment groups was similar in the patient-level responder analysis, but numerically favored alg+pbo in the group-level analysis (35% responders in both arms; P = 0.95; and LS mean difference -0.8; P = 0.48). Self-care, usual activities, and depression/anxiety domains of EQ-5D-5L numerically favored cipa+mig in both analyses (e.g. 20 vs. 12% responders in the cipa+mig vs. alg+pbo arm for EQ-5D-5L self-care; P = 0.54; and LS mean difference -0.108; P = 0.52)., Conclusions: Overall, switching treatment from alglucosidase alfa to cipa+mig positively impacted PRO measurements during the double-blind period of PROPEL., Trial Registration: NCT03729362; Registration date: November 1, 2018; https://clinicaltrials.gov/study/NCT03729362., Competing Interests: Declarations Ethics approval and consent to participate PROPEL was approved by the appropriate independent ethics committees and institutional review boards at each study site and was conducted according to international guidelines for clinical studies, such as the Declaration of Helsinki and Good Clinical Practice Guidelines. All participants provided written informed consent before participating in the study. Consent for publication Not applicable. Competing interests KGC received research funding from Alnylam, Biogen, Pfizer, Roche, Sanofi Genzyme; advisory board member honoraria from Alexion, Alnylam, Amicus Therapeutics, Inc., argenx, Biogen, Ipsen, Janssen Pharmaceutics, Lupin, Pfizer, Roche, Sanofi Genzyme and UCB; and is Chairholder of the Emil von Behring Chair for Neuromuscular and Neurodegenerative Disorders by CSL Behring. BJB reports consultant/advisory board membership for Pfizer, Amicus Therapeutics, Inc., and Sanofi; and owns stocks in Lacerta Therapeutics. JD-M reports consulting fees/honoraria from Sarepta, Sanofi, Audentes; has received grant support from Sanofi, Spark and Boehringer Ingelheim; and payment for speaking from Sanofi, Sarepta and Lupin. MMD serves or recently served as a consultant for Abata/Third Rock, Abcuro, Amicus Therapeutics, Inc., argenx, Astellas, Cabaletta Bio, Catalyst, CNSA, Covance/Labcorp, CSL Behring, Dianthus, Horizon, EMD Serono/Merck, Ig Society, Inc, Janssen Pharmaceuticals, Medlink, Octapharma, Priovant, Sanofi Genzyme, Shire Takeda, TACT/Treat NMD, UCB Biopharma, Valenza Bio and Wolters Kluwer Health/UpToDate; and has received research grants or contracts, or educational grants from Alexion/AstraZeneca, Alnylam Pharmaceuticals, Amicus Therapeutics, Inc., argenx, Bristol-Myers Squibb, Catalyst, CSL Behring, FDA/OOPD, GlaxoSmithKline, Genentech, Grifols, Mitsubishi Tanabe Pharma, MDA, NIH, Novartis, Octapharma, Orphazyme, Ra Pharma/UCB, Sanofi Genzyme, Sarepta Therapeutics, Shire Takeda, Spark Therapeutics, The Myositis Association, and UCB Biopharma/RaPharma. PSK has received research/grant support from Sanofi Genzyme and Amicus Therapeutics, Inc., and has received consulting fees and honoraria from Sanofi Genzyme, Amicus Therapeutics, Inc., JCR Pharmaceuticals, Bayer and Asklepios Biopharmaceutical, Inc. (AskBio). She is a member of the Pompe and Gaucher Disease Registry Advisory Board for Sanofi Genzyme, Pompe Disease Advisory Board for Amicus Therapeutics, Inc., and Advisory Board for Baebies. She has held equity in Asklepios Biopharmaceuticals and may receive milestone payments related to that equity in the future. HK served as a consultant for Alexion AstraZeneca Rare disease, argenx, UCB, Immunovant, Sanofi, and has received research grants or educational grants from Sanofi, MDA, and Healey ALS platform trial. TM has participated in an advisory capacity for Abbvie, Alexion, Amicus Therapeutics, Inc., Annji, argenx, Arvinas, Audentes, Cabaletta, Maze Therapeutics, Momenta, Ra Pharmaceuticals, Sanofi Genzyme, Sarepta, Spark Therapeutics, and UCB. He is a member of the medical advisory board for the Myositis Association, Neuromuscular Disease Foundation, Myasthenia Gravis Foundation of California and Myasthenia Gravis Foundation of America. He has received research funding from the Myositis Association, the Muscular Dystrophy Association, the NIH and from the following sponsors: Alexion, Amicus Therapeutics, Inc., Annji, argenx, Audentes, Bristol-Myers Squib, Cabaletta, Cartesian Therapeutics, Grifols, Momenta, Ra Pharmaceuticals, Sanofi Genzyme, Spark Therapeutics, UCB, and Valerion. He is a member of the data safety monitoring board for Acceleron, Applied Therapeutics, Sarepta, and the NIH. MR has received honoraria for educational symposia from Sanofi Genzyme and Amicus Therapeutics, Inc., and for participation on advisory boards for Sanofi, and Amicus Therapeutics, Inc. BS has received unrestricted research grants from Amicus Therapeutics, Inc., Astellas, Roche, Marigold Foundation, AMDA Foundation and speaker’s honoraria from Amicus Therapeutics, Inc., Alexion, Kedrion, and Sanofi. He has participated as a scientific adviser for Amicus Therapeutics, Inc., argenx, Astellas, Bayer, Maze, Pepgen, Sanofi, and Spark. He declares no stocks or shares. NH and AK are employees of Certara, which is a paid consultant to Amicus Therapeutics, Inc. FH and SS are employees of and hold stock in Amicus Therapeutics, Inc. AT has received honorarium for educational talks from Sanofi Genzyme and Amicus Therapeutics, Inc. and for participation on advisory boards for Sanofi, Amicus Therapeutics, Inc., Aro and Spark. He is a member of the European Reference Network for Neuromuscular Disorders (EU-NMD)– Project ID 739543., (© 2024. The Author(s).)

Infantile-onset Pompe disease (IOPD) is caused by a deficiency in the enzyme acid alpha-glucosidase (GAA). It is characterized by severe and progressive hypertrophic cardiomyopathy and muscle weakness with death in the first 2 years of life if left untreated. Enzyme replacement therapy (ERT) with alglucosidase-alfa is lifesaving, but its effectiveness is influenced by the patient's cross-reactive immunologic material (CRIM) status, dose of ERT, and the development of high antibody titers, which can reduce the therapy's efficacy. The inability of CRIM-negative IOPD patients to produce native GAA exposes them to a high risk of development of anti-rhGAA IgG antibody titers, leading to treatment failure. We present the case of CRIM-negative dizygotic twins treated with high-dose alglucosidase-alfa (40 mg/kg/week), initiated at 28 days (Twin A) and 44 days (Twin B). Both twins received immune tolerance induction (ITI) with rituximab, methotrexate, and IVIG to mitigate antibody response. Initial evaluations revealed elevated left ventricular mass index (LVMI) and elevated biomarkers (urine glucose tetrasaccharide (Glc 4 ), creatine kinase (CK), and aspartate aminotransferase (AST)) in both twins. Following treatment, cardiac function and biomarkers normalized within several months, with a slight delay in Twin B compared to Twin A, likely attributed to the later initiation of ERT. Both twins safely tolerated ITI, achieving immune tolerance with low antibody titers. At 28 months, the twins transitioned to avalglucosidase-alfa (40 mg/kg every other week (EOW)), which was well tolerated without an increase in antibody titers. At 39 months, both twins exhibited normal cardiac function, LVMI, and biomarkers. Motor skills continued to improve, though some kinematic concerns persisted. These cases underscore the importance of early, high-dose ERT combined with ITI in managing CRIM-negative IOPD. While transitioning to avalglucosidase-alfa at 40 mg/kg/EOW was beneficial and well-tolerated in our patients, further studies are needed to confirm its long-term efficacy compared to the high-dose weekly 40 mg/kg alglucosidase-alfa., Competing Interests: Priya S. Kishnani reports a relationship with Sanofi Genzyme that includes: board membership, consulting or advisory, and funding grants. Priya S. Kishnani reports a relationship with Amicus Therapeutics Inc. Research & Gene Therapy Center of Excellence that includes: board membership, consulting or advisory, and funding grants. Priya S. Kishnani reports a relationship with Maze Therapeutics Inc. that includes: consulting or advisory and equity or stocks. Priya S. Kishnani reports a relationship with Asklepios BioPharmaceutical Inc. that includes: consulting or advisory and equity or stocks. Priya S. Kishnani reports a relationship with Babies that includes: board membership. Ankit K. Desai reports a relationship with Sanofi Genzyme that includes: funding grants. Ankit K. Desai reports a relationship with Lysosomal Storage Network that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Inc.)

Gaucher disease (GD) type 3 is an autosomal recessive lysosomal disease caused by deficiency of β-glucocerebrosidase (GCase) and encompasses a spectrum of cardiac, neurological, and ophthalmological abnormalities. Although the clinical presentations can be diverse, a recognized clinical trajectory points to an early onset, predominantly before 18 years. GD type 3c is primarily caused by homozygosity for GBA pathogenic variant c.1342G>C (p.Asp448His; historically referred to as D409H) and includes visceral, hematological, skeletal, and cardiac abnormalities. Notably, GD type 3c is distinct from other GD types because it is primarily characterized by valvular heart disease. Yet, with less than 50 patients with GD type 3c reported to date, the phenotypic spectrum and extent of cardiac involvement remains ill-defined. We present a 20-year-old female with an atypical presentation of GD type 3c consisting of chronic intermediate uveitis as the presenting feature and the presence of extensive polyneuropathy starting in adolescence which has been previously unreported in GD type 3c. Distinctively, she has maintained normal cardiac function. Moreover, we compare our case with those reported in the literature to broaden awareness of the varied initial presentations of this disease. The diverse presentations seen in GD type 3c, underscored by our case and those previously reported, demonstrate the need for standardized evaluation and management protocols., Competing Interests: John S. Wang, Rebecca L. Koch, Daniel Kenney‐Jung, Erin Huggins, Sirajbir S. Sodhi, Andrew P. Landstrom, Dilraj S. Grewal, and Priya S. Kishnani declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Priya S. Kishnani has received honoraria and grant support from Sanofi and Takeda Pharmaceuticals., (© 2024 The Author(s). JIMD Reports published by John Wiley & Sons Ltd on behalf of SSIEM.)

Gaucher disease type 1 (GD1) is known for phenotypic heterogeneity and varied natural history. Registrational clinical trials enrolled narrowly defined phenotypes, but greater diversity is encountered in clinical practice. We report real-world outcomes with long-term eliglustat treatment in adults with GD1 in the International Collaborative Gaucher Group Gaucher Registry. Among 5985 GD1 patients in the Registry as of January 6, 2023, 872 started eliglustat at ≥18 years old; of these, 469 met inclusion criteria. We compared clinical parameters at eliglustat initiation (i.e., baseline) and follow-up in treatment-naïve patients and used linear mixed models to estimate annual change from baseline in parameters among patients who switched to eliglustat after ≥1 year on enzyme replacement therapy. Over 4 years of follow-up in non-splenectomized treatment-naïve patients, hemoglobin and platelet count increased, liver and spleen volume decreased, and total lumbar spine bone mineral density (BMD) Z-score decreased slightly. Among non-splenectomized switch patients, on average, hemoglobin decreased -0.030 (95% CI: -0.053, -0.008) g/dL (N = 272) and platelet count increased 2.229 (95% CI: 0.751, 3.706) × 10 3 /mm 3 (N = 262) annually up to 10 years; liver volume decreased (-0.009 [95% CI: -0.015, -0.003] MN) (N = 102) and spleen volume remained stable (-0.070 [95% CI: -0.150, 0.010] MN) (N = 106) annually up to 7 years; and total lumbar spine BMD Z-score increased 0.041 (95% CI: 0.015, 0.066) (N = 183) annually up to 8 years. Among splenectomized switch patients, clinical parameters were stable over time. These long-term, real-world outcomes are consistent with the eliglustat clinical trials and emerging real-world experience across the GD phenotypic spectrum., (© 2024 The Authors. American Journal of Hematology published by Wiley Periodicals LLC.)

Background: Biochemical testing is a common first-tier approach in the setting of genetic evaluation of patients with unexplained developmental delay. However, results can be unclear, and a plan for second-tier analysis must be determined based on the patient's biochemical results and clinical presentation - in many cases, triggering a diagnostic odyssey., Case Presentation: A male patient from the United States presenting with unexplained developmental delay, microcephaly, hypotonia, and feeding difficulties was referred for clinical genetic evaluation at age 8 months. Biochemical testing revealed an isolated marked elevation of glutaric acid on urine organic acid profile, without elevations of related metabolites. Further testing included GCDH sequencing, a neurometabolic gene panel, chromosomal microarray, Prader Willi/Angelman testing, and lysosomal disease enzyme panel, all of which were non-diagnostic. The patient had persistent developmental delay and hypotonia, dystonia, sensorineural hearing loss, and abnormal brain myelination on magnetic resonance imaging. Whole exome sequencing (WES) was performed and revealed a dual diagnosis of glutaric aciduria III (GA III) and BCAP31- related disorder, an X-linked intellectual disability syndrome, caused by a novel pathogenic variant., Conclusions: GA III has historically been considered clinically benign, with few reported cases. This patient's presenting symptoms were similar to those commonly seen in GA I and GA II, however the biochemical abnormalities were not consistent with these disorders, prompting additional molecular and biochemical testing. Ultimately, WES confirmed a diagnosis of BCAP31 -related syndrome, a rare neurological disorder, which explained the patient's presenting symptoms. WES also identified a secondary diagnosis of GA III. We present a patient with two rare genetic conditions, highlighting the importance of deep phenotyping and the utility of WES in the setting of a patient with dual genetic diagnoses., Competing Interests: The authors have no competing interests as defined by MGM, or other interests that might be perceived to influence the results and/or discussion reported in this paper., (© 2024 The Authors. Published by Elsevier Inc.)

BackgroundGlycogen storage disease type IV (GSD IV) is an ultrarare autosomal recessive disorder that causes deficiency of functional glycogen branching enzyme and formation of abnormally structured glycogen termed polyglucosan. GSD IV has traditionally been categorized based on primary hepatic or neuromuscular involvement, with hepatic GSD IV subclassified as discrete subtypes: classic (progressive) and nonprogressive.MethodsTo better understand the progression of liver disease in GSD IV, we present clinical and histopathology data from 23 patients from around the world and characterized the liver involvement in the Gbe1ys/ys knockin mouse model.ResultsWe propose an alternative to the established subtype-based terminology for characterizing liver disease in GSD IV and recognize 3 tiers of disease severity: (i) "severe progressive" liver disease, (ii) "intermediate progressive" liver disease, and (iii) "attenuated" liver disease. Analysis of liver pathology revealed that risk for liver failure cannot be predicted from liver biopsy findings alone in individuals affected by GSD IV. Moreover, analysis of postmortem liver pathology from an individual who died over 40 years after being diagnosed with nonprogressive hepatic GSD IV in childhood verified that liver fibrosis did not regress. Last, characterization of the liver involvement in a mouse model known to recapitulate the adult-onset neurodegenerative form of GSD IV (Gbe1ys/ys mouse model) demonstrated hepatic disease.ConclusionOur findings challenge the established subtype-based view of GSD IV and suggest that liver disease severity among patients with GSD IV represents a disease continuum.Trial registrationClinicalTrials.gov NCT02683512FundingNone.

Introduction: Pompe disease, a lysosomal storage disorder, is characterized by acid α-glucosidase (GAA) deficiency and categorized into two main subtypes: infantile-onset Pompe disease (IOPD) and late-onset Pompe disease (LOPD). The primary treatment, enzyme replacement therapy (ERT) with recombinant human GAA (rhGAA), faces challenges due to immunogenic responses, including the production of anti-drug antibody (ADA), which can diminish therapeutic efficacy. This study aims to assess the effectiveness of immune tolerance induction (ITI) therapy in cross-reactive immunologic material (CRIM)-positive Pompe disease patients with established high ADA levels., Method: In a single-center, open-label prospective study, we assessed ITI therapy's efficacy in Pompe disease patients, both IOPD and LOPD, with persistently elevated ADA titers (≥1:12,800) and clinical decline. The ITI regimen comprised bortezomib, rituximab, methotrexate, and intravenous immunoglobulin. Biochemical data, biomarkers, ADA titers, immune status, and respiratory and motor function were monitored over six months before and after ITI., Results: This study enrolled eight patients (5 IOPD and 3 LOPD). After a 6-month ITI course, median ADA titers significantly decreased from 1:12,800 (range 1:12,800-1:51,200) to 1:1,600 (range 1:400-1:12,800), with sustained immune tolerance persisting up to 4.5 years in some cases. Serum CK levels were mostly stable or decreased, stable urinary glucose tetrasaccharide levels were maintained in four patients, and no notable deterioration in respiratory or ambulatory status was noted. Adverse events included two treatable infection episodes and transient symptoms like numbness and diarrhea., Conclusion: ITI therapy effectively reduces ADA levels in CRIM-positive Pompe disease patients with established high ADA titers, underscoring the importance of ADA monitoring and timely ITI initiation. The findings advocate for personalized immunogenicity risk assessments to enhance clinical outcomes. In some cases, prolonged immune suppression may be necessary, highlighting the need for further studies to optimize ITI strategies for Pompe disease treatment. ClinicalTrials.gov NCT02525172; https://clinicaltrials.gov/study/NCT02525172., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Chen, Hsu, Fang, Desai, Lee, Hwu, Tsai, Kishnani and Chien.)

Background: Hypophosphatasia (HPP) is a rare inherited disease caused by deficient activity of tissue-nonspecific alkaline phosphatase. Many adults with HPP have a high burden of disease, experiencing chronic pain, fatigue, limited mobility, and dental issues, contributing to decreased health-related quality of life (HRQoL). HPP may be treated with the enzyme replacement therapy asfotase alfa though real-world data in adults are limited. This analysis was conducted to assess the clinical effectiveness of asfotase alfa among adults in the Global HPP Registry., Methods: The Global HPP Registry is an observational, prospective, multinational study. Adults ≥ 18 years of age were included in this analysis if they had serum alkaline phosphatase (ALP) activity below the age- and sex-adjusted reference ranges, and/or ALPL variant(s), and received asfotase alfa for ≥ 6 months. Mobility was assessed with the 6-Minute Walk Test (6MWT), and patient-reported outcomes tools were used to assess pain (Brief Pain Inventory-Short Form), quality of life (36-item Short Form Health Survey, version 2 [SF-36v2]), and disability (Health Assessment Questionnaire-Disability Index) at multiple time points from baseline through Month 36. Data were collected as per usual standard of care; patients may not have contributed data at all time points., Results: A total of 190 patients met the inclusion criteria. For patients with ≥ 1 follow-up measurement, the mean distance achieved on 6MWT increased from 404 m (range 60-632 m) at baseline (n = 31) to 484 m at Month 12 (range 240-739 m; n = 18) and remained above baseline through Month 36 (n = 7). Improvements in mean self-reported pain severity scores ranged from - 0.72 (95% CI: - 1.23, - 0.21; n = 38) to - 1.13 (95% CI: - 1.76, - 0.51; n = 26) and were observed at all time points. Improvements in the Physical Component Summary score of SF-36v2 were achieved by Month 6 and sustained throughout follow-up. There was a trend toward improvement in the Mental Component Summary score of SF-36v2 at most time points, with considerable fluctuations from Months 12 (n = 28) through 36 (n = 21). The most frequent adverse events were injection site reactions., Conclusions: Adults with HPP who received asfotase alfa for ≥ 6 months experienced improvements in mobility, physical function, and HRQoL, which were maintained over 3 years of follow-up., Registration: NCT02306720; EUPAS13514., (© 2024. The Author(s).)

Introduction: High sustained anti-rhGAA antibody titers (HSAT; ≥12,800) are directly linked to reduced efficacy of enzyme replacement therapy (ERT) and subsequent clinical deterioration in infantile-onset Pompe disease (IOPD). We have previously demonstrated the safety and effectiveness of a bortezomib-based immune-tolerance induction (ITI) regimen (bortezomib, rituximab, methotrexate, and IVIG) in eliminating HSAT., Methods: Here, we describe two IOPD cases (patients 6 and 8) who developed HSAT at 8 and 10 weeks on ERT despite transient low-dose methotrexate ITI administration in the ERT-naïve setting and were treated with a bortezomib-based ITI regimen, and we compare their courses to a series of six historical patients (patients 1-5, and 7) with a similar presentation who exemplify our evolving approach to treatment., Results: In total, patients 6 and 8 received 16 and 8 doses of bortezomib (4 doses=1 cycle) respectively reducing titers from 25,600 to seronegative, but differences in the course of their therapy were instructive regarding the optimal approach to initial treatment of HSAT; specifically, patient 6 was treated initially with only a single course of bortezomib rescue therapy, while patient 8 received two back-to-back courses. Patient 8 received IVIG therapy throughout the immunosuppression whereas patient 6 received IVIG therapy and was switched to subcutaneous IgG replacement. Patient 6 had a transient reduction in anti-rhGAA antibodies, after receiving a single initial cycle of bortezomib, but had a recurrence of high anti-rhGAA antibody titer after 160 weeks that required 3 additional cycles of bortezomib to ultimately achieve tolerance. In contrast, patient 8 achieved tolerance after being given two consecutive cycles of bortezomib during their initial treatment and had B cell recovery by week 54. Since the reduction in anti-rhGAA antibodies, both patients are doing well clinically, and have decreasing ALT, AST, and CK. No major infections leading to interruption of treatment were observed in either patient. The bortezomib-based ITI was safe and well-tolerated, and patients continue to receive ERT at 40 mg/kg/week., Discussion: These case studies and our previous experience suggest that to achieve an effective reduction of anti-rhGAA antibodies in the setting of HSAT, bortezomib should be initiated at the earliest sign of high anti-rhGAA antibodies with a minimum of two consecutive cycles as shown in the case of patient 8. It is important to note that, despite initiation of ERT at age 2.3 weeks, patient 8 quickly developed HSAT. We recommend close monitoring of anti-rhGAA antibodies and early intervention with ITI as soon as significantly elevated anti-rhGAA antibody titers are noted., Competing Interests: AD has received grant support from Sanofi Genzyme and the Lysosomal Disease Network. AD has received honoraria from Sanofi Genzyme. CG has received Honoraria from Sanofi, Amicus Therapeutics, and RegenX Bio. RW serves on the Scientific Advisory Board for and owns equity in M6P Therapeutics. PK has received research/grant support from Sanofi Genzyme and Amicus Therapeutics. PK has received consulting fees and honoraria from Sanofi Genzyme, Amicus Therapeutics, Maze Therapeutics, Bayer, and Asklepios Biopharmaceutical, Inc. (AskBio). PK is a member of the Pompe and Gaucher Disease Registry Advisory Board for Sanofi Genzyme, Pompe Disease Advisory Board for Amicus Therapeutics, and Advisory Board for Babies. PK has equity with Maze Therapeutics and has held equity in Asklepios Biopharmaceuticals and may receive milestone payments related to that equity in the future. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be constructed as a potential conflict of interest., (Copyright © 2024 Desai, Shrivastava, Grant, Wang, Burt and Kishnani.)

Background: Thousands of genetic variants have been identified in cardiomyopathy-associated genes. Diagnostic genetic testing is key for evaluation of individuals with suspected cardiomyopathy. While accurate variant pathogenicity assignment is important for diagnosis, the frequency of and factors associated with clinically relevant assessment changes are unclear., Objectives: The authors aimed to characterize pathogenicity assignment change in cardiomyopathy-associated genes and to identify factors associated with this change., Methods: We identified 10 sarcomeric and 6 desmosomal genetic cardiomyopathy-associated genes along with comparison gene sets. We analyzed clinically meaningful changes in pathogenicity assignment between any of the following: pathogenic/likely pathogenic (P/LP), conflicting interpretations of pathogenicity or variant of unknown significance (C/VUS), and benign/likely benign. We explored association of minor allele frequency (MAF) differences between well, and traditionally poorly, represented ancestries in genetic studies with assessment stability. Analyses were performed using ClinVar and GnomAD data., Results: Of the 30,975 cardiomyopathy-associated gene variants in ClinVar, 2,276 of them (7.3%) had a clinically meaningful change in pathogenicity assignment over the study period, 2011 to 2021. Sixty-seven percent of variants that underwent a clinically significant change moved from P/LP or benign/likely benign to C/VUS. Among cardiomyopathy variants downgraded from P/LP, 35% had a MAF above 1 × 10 -4 in non-Europeans and below 1 × 10 -4 in Europeans., Conclusions: Over the past 10 years, 7.3% of cardiomyopathy gene variants underwent a clinically meaningful change in pathogenicity assignment. Over 30% of downgrades from P/LP may be attributable to higher MAF in Non-Europeans than Europeans. This finding suggests that low ancestral diversity in genetic studies has increased diagnostic uncertainty in cardiomyopathy gene variants.

Background: The construct validity and interpretation of the Patient-Reported Outcome Measurement Information System (PROMIS ® ) Physical Function short form 20a (PF20a) questionnaire were evaluated for patients with late-onset Pompe disease (LOPD), a rare, autosomal recessive, progressive neuromuscular disorder treatable by enzyme replacement therapy (ERT)., Methods: In the phase 3 PROPEL study, adults with LOPD underwent testing of physical functioning and had PRO measurements at baseline and at weeks 12, 26, 38, and 52 while receiving experimental or standard-of-care ERT. All patients were pooled for analyses, without comparisons between treatment groups. Associations and correlations between PROMIS PF20a scores and the 6-minute walk distance (6MWD), % predicted forced vital capacity (FVC), manual muscle test (MMT) of the lower extremities, Gait, Stairs, Gowers' maneuver, Chair (GSGC) score, and Rasch-built Pompe-specific Activity (R-PAct) scale were evaluated by calculating regression coefficients in linear regression models and Pearson correlation coefficients (R); patients' age, sex, race, ERT prior to study, body mass index, and study treatment were included as covariables. The minimal clinically important difference (MCID) of PROMIS PF20a was determined using distribution- and anchor-based methods., Results: 123 patients received at least 1 dose of ERT. In multivariable analyses, PROMIS PF20a scores had strong correlations with R-PAct scores (R = 0.83 at baseline and R = 0.67 when evaluating changes between baseline and 52 weeks) and moderate correlations with the 6MWD (R = 0.57 at baseline and R = 0.48 when evaluating changes between baseline and 52 weeks). Moderate correlations were also observed between PROMIS PF20a and MMT (R = 0.54), GSGC (R=-0.51), and FVC (R = 0.48) at baseline. In multivariable linear regression models, associations were significant between PROMIS PF20a and 6MWD (P = 0.0006), MMT (P = 0.0034), GSGC (P = 0.0278), and R-PAct (P < 0.0001) at baseline, between PROMIS PF20a and 6MWD (P < 0.0001), FVC (P = 0.0490), and R-PAct (P < 0.0001) when combining all measurements, and between PF20a and 6MWD (P = 0.0016) and R-PAct (P = 0.0001) when evaluating changes in scores between baseline and 52 weeks. The anchor-based and distribution-based MCID for a clinically important improvement for PROMIS PF20a were 2.4 and 4.2, respectively., Conclusions: PROMIS PF20a has validity as an instrument both to measure and to longitudinally follow physical function in patients with LOPD., Trial Registration: ClinicalTrials.gov, NCT03729362. Registered 2 November 2018, https://www., Clinicaltrials: gov/search?term=NCT03729362 ., (© 2024. The Author(s).)

Introduction: The efficacy of enzyme replacement therapy (ERT) with alglucosidase alfa for infantile-onset Pompe disease (IOPD) is limited in some patients due to the development of high and sustained antibody titers (HSAT; ≥12,800)., Methods: We carried out detailed immunophenotyping of IOPD patients (n=40), including analysis of circulating cell populations by flow cytometry and plasma cytokines by multiplex array, to determine whether patients with HSAT have unique immunological characteristics compared to those with low titers (LT; <12,800)., Results: Compared to patients with LT, patients who develop HSAT were skewed toward a type 2 immune profile, with an increased frequency of Th2 cells that was positively correlated with levels of Th2 (IL-4, IL-5, IL-13) and pro-inflammatory (IL-6, TNF-α, MIP-1α, MIP-1β) cytokines. B cells were increased in HSAT patients with a decreased fraction of unswitched memory B cells. Plasma GM-CSF concentrations were lower on average in HSAT patients, while CXCL11 was elevated. Finally, using principal components analysis, we derived an HSAT Signature Score that successfully stratified patients according to their antibody titers., Discussion: The immune profiles revealed in this study not only identify potential biomarkers of patients that developed HSAT but also provide insights into the pathophysiology of HSAT that will ultimately lead to improved immunotherapy strategies., Competing Interests: AD has received grant support from Sanofi Genzyme and the Lysosomal Disease Network. AD has received honoraria from Sanofi Genzyme. PK has received research/grant support from Sanofi Genzyme and Amicus Therapeutics. PK has received consulting fees and honoraria from Sanofi Genzyme, Amicus Therapeutics, Maze Therapeutics, Bayer, and Asklepios Biopharmaceutical, Inc. AskBio. PK is a member of the Pompe and Gaucher Disease Registry Advisory Board for Sanofi Genzyme, Pompe Disease Advisory Board for Amicus Therapeutics, and Advisory Board for Baebies. PK has equity with Maze Therapeutics and has held equity in Asklepios Biopharmaceuticals, and may receive milestone payments related to that equity in the future. AR is on the Medical Advisory Board of Sonoma Biotherapeutics, and the Scientific Advisory Boards of 4DMT and the Alice and YT Chen Genetics and Genomics Center and is a Consultant for EpiVax, Inc. AR is employed by Epivax, Inc. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Desai, Smith, Yi, Rosenberg, Burt and Kishnani.)

Background: Studies indicate that doses of alglucosidase alfa (ALGLU) higher than label dose (20 mg/kg every other week) improve clinical outcomes in infantile-onset Pompe disease (IOPD). We investigated data from the Pompe Registry to determine the association between ALGLU dose and survival in IOPD., Results: We included 332 IOPD patients from the Registry as of January 2022 who had cardiomyopathy and were first treated at age < 1 year. We used Cox proportional hazards models to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association between ALGLU as a time-varying exposure and survival, adjusting for age at first treatment, sex, and cross-reactive immunologic material (CRIM)/immune tolerance induction (ITI) status. Dose was measured as average relative dose received over time (in multiples of label dose, range > 0 to 4 times label dose), current dose, and lagged dose. 81% patients received label dose at treatment initiation. Over time, 52% received a higher dose. Higher ALGLU dose over time was associated with improved survival: adjusted HR 0.40 (95% CI 0.22-0.73, p = 0.003) per 1-unit increase in average relative dose, with similar results for invasive ventilation-free survival (adjusted HR 0.48, 95% CI 0.28-0.84; p = 0.010). The association was consistent in patients first treated before or after 3 months of age and did not vary significantly by CRIM status. Results for current and lagged dose were similar to average dose., Conclusions: Higher ALGLU doses were associated with significantly improved overall and invasive ventilator-free survival in IOPD. Results were consistent across sensitivity analyses., (© 2023. The Author(s).)

Background and Objectives: The Pompe Disease Symptom Scale (PDSS) and Impact Scale (PDIS) were created to measure the severity of symptoms and functional limitations experienced by patients with late-onset Pompe disease (LOPD). The objectives of this analysis were to establish a scoring algorithm and to examine the reliability, validity, and responsiveness of the measures using data from the COMET clinical trial., Methods: The COMET trial was a randomized, double-blind study comparing the efficacy and safety of avalglucosidase alfa and alglucosidase alfa in patients with LOPD aged 16-78 years at baseline. Adult participants (18 years or older) completed the PDSS and PDIS daily for 14 days at baseline and for 2 weeks before quarterly clinic visits for 1 year after randomization using an electronic diary. Data were pooled across treatment groups for the current analyses. Factor analysis and inter-item correlations were used to derive a scoring algorithm. Test-retest and internal consistency analyses examined the reliability of the measures. Correlations with criterion measures were used to evaluate validity and sensitivity to change. Anchor and distribution-based analyses were conducted to estimate thresholds for meaningful change., Results: Five multi-item domain scores were derived from the PDSS (Shortness of Breath, Overall Fatigue, Fatigue/Pain, Upper Extremity Weakness, Pain) and 2 from the PDIS (Mood, Difficulty Performing Activities). Internal consistency (Cronbach α > 0.90) and test-retest reliability (intraclass correlation >0.60) of the scores were supported. Cross-sectional and longitudinal correlations with the criterion measures generally supported the validity of the scores ( r > 0.40). Within-patient meaningful change estimates ranging from 1.0 to 1.5 points were generated for the PDSS and PDIS domain scores., Discussion: The PDSS and PDIS are reliable and valid measures of LOPD symptoms and functional impacts. The measures can be used to evaluate burden of LOPD and effects of treatments in clinical trials, observational research, and clinical practice., Trial Registration Information: ClinicalTrials.gov identifier: NCT02782741., Competing Interests: M.M. Dimachkie has received consulting fees from Abata/Third Rock, Abcuro, Amazentis, ArgenX, Astellas, Catalyst, Cello, Covance/Labcorp, CSL-Behring, EcoR1, Janssen, Kezar, MDA, Medlink, Momenta, NuFactor, Octapharma, Priovant, RaPharma/UCB, Roivant Sciences Inc, Sanofi, Scholar Rock, Shire Takeda, Spark Therapeutics, TACT, UCB Biopharma, and UpToDate. M.M. Dimachkie has undertaken contracted research for or received unrestricted educational grants from Alexion, Alnylam Pharmaceuticals, Amicus, Biomarin, Bristol-Myers Squibb, Catalyst, Corbus, CSL-Behring, FDA/OOPD, GlaxoSmithKline, Genentech, Grifols, Kezar, Mitsubishi Tanabe Pharma, MDA, NIH, Novartis, Octapharma, Orphazyme, Ra Pharma/UCB, Sanofi, Sarepta Therapeutics, Shire Takeda, Spark Therapeutics, The Myositis Association, TMA, UCB Biopharma/RaPharma, and Viromed/Healixmith. P.S. Kishnani has received research/grant support from Sanofi and Amicus Therapeutics and has received consulting fees and honoraria from Sanofi, Amicus Therapeutics, Maze Therapeutics, JCR Pharmaceutical, and Asklepios Biopharmaceutical, Inc. (AskBio). P.S. Kishnani is a member of the Pompe and Gaucher Disease Registry Advisory Boards for Sanofi, Amicus Therapeutics, and Baebies. P.S. Kishnani has equity in Asklepios Biopharmaceutical, Inc. (AskBio), and Maze Therapeutics. C. Ivanescu is an employee of IQVIA. G. Flore was an employee of IQVIA at the time of study participation. C. Gwaltney has received consulting fees from Sanofi. N.A.M.E. van der Beek has received consulting fees and travel reimbursement from Sanofi and Amicus Therapeutics. A. Hamed is an employee of Sanofi. K. An Haack and her spouse are employees of Sanofi. L. Pollissard is an employee of Sanofi. E. Baranowski was an employee of Sanofi at the time of study participation. S.E. Sparks is an employee of Sanofi. P. DasMahapatra is an employee of Sanofi. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/cp., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)

Late-onset Pompe disease (LOPD) is a multisystem disorder with significant myopathy. The standard treatment is enzyme replacement therapy (ERT), a therapy that is lifesaving, yet with limitations. Clinical trials have emerged for other potential treatment options, including adeno-associated virus (AAV) gene therapy. We present clinical parameters and AAV antibody titers for 19 individuals with LOPD undergoing screening for a Phase I clinical trial with an AAV serotype 8 vector targeting hepatic transduction (AAV2/8-LSPhGAA). Reported clinical parameters included GAA genotype, assessments of muscle function, upright and supine spirometry, anti-recombinant human GAA antibody titers, and biomarkers. Variability in measured parameters and phenotypes of screened individuals was evident. Eligibility criteria required that all participants have six-minute walk test (6MWT) and upright forced vital capacity (FVC) below the expected range for normal individuals, and were stably treated with ERT for >2 years. All participants had Pompe disease diagnosed by enzyme deficiency, and all had the common c.-32-13T>G LOPD pathogenic variant. Screening identified 14 patients (74%) with no or minimal detectable neutralizing antibodies against AAV8 (titer ≤1:5). 6MWT distance varied significantly (percent of expected distance ranging from 24% to 91% with an average of 60 and standard deviation of 21). Upright FVC percent predicted ranged from 35% predicted to 91% predicted with an average of 66 and standard deviation of 18. None of the participants had significantly elevated alanine transaminase, which has been associated with LOPD and could complicate screening for hepatitis related to AAV gene therapy. We review the parameters considered in screening for eligibility for a clinical trial of AAV8 vector-mediated gene therapy., Competing Interests: Dr. Dwight D. Koeberl and Dr. Priya S. Kishnani have developed the technology that is being used in the study. If the technology is commercially successful in the future, the developers and Duke University may benefit financially. Dr. Dwight D. Koeberl has served as a consultant for Sangamo Therapeutics and for Genzyme Sanofi, Amicus, and Vertex; has received grant support from Viking Therapeutics, Genzyme Sanofi, Roivant Rare Diseases, and Amicus; and has equity in Askbio, which is developing gene therapy for Pompe disease. Dr. William B. Hannah has received consulting fees from PTC Therapeutics and ReCode Therapeutics. Dr. Edward C. Smith received salary support for his role as PI on this study. Dr. Laura E. Case has received honoraria from Genzyme Sanofi and Amicus, has participated in research supported by Genzyme Sanofi, Amicus, AskBio, Valerion, Biomarin, and by Roivant Sciences; and is a member of the Pompe Registry North American Board of Advisors Genzyme Sanofi. Dr. Deeksha Bali has received research grant support and travel funds from Genzyme Sanofi, Baebies Inc., Biomarin, Alexion Inc., SOBI biopharma, and JCR biopharma. Dr. Priya S. Kishnani has received research/grant support from Sanofi Genzyme and Amicus Therapeutics. She received consulting fees and honoraria from Sanofi Genzyme, Amicus Therapeutics, Maze Therapeutics, JCR Pharmaceutical, and Asklepios Biopharmaceutical, Inc. (AskBio). She is a member of the Pompe and Gaucher Disease Registry Advisory Board for Sanofi Gezyme, Amicus Therapeutics, and Baebies. Dr. Priya S. Kishnani has equity in Asklepios Biopharmaceutical, Inc. (AskBio) which is developing gene therapy for Pompe disease and has equity in Maze Therapeutics which is developing a small molecule therapy for Pompe disease., (© 2023 The Authors. JIMD Reports published by John Wiley & Sons Ltd on behalf of SSIEM.)

Importance: Implementation of newborn screening (NBS) in the United States now detects infants with late-onset Pompe disease (LOPD), a lysosomal storage disease characterized by slowly progressive muscle weakness, and detailed clinical evaluation has identified early muscle weakness. Biomarkers may be uninformative; thus, non-invasive imaging is needed to assess early LOPD muscle changes. Muscle ultrasound (US) measuring echointensity (EI) is a non-invasive measure of muscle health., Objective: In this study, we aimed to evaluate if EI can identify characteristic patterns of muscle involvement in LOPD patients identified by NBS., Design/setting: Prospective, cross-sectional, single time point study., Setting: One-center study., Participants: We examined 20 infants with NBS-identified LOPD (ages 5-20 months). All had standardized physical therapy assessments., Exposures: Creatine Kinase (CK) and Urine Hexose Tetrasaccharide (Glc4) were obtained. Muscle US of deltoid, biceps brachii, forearm flexors, thoracic paraspinals, gluteus maximus, quadriceps, tibialis anterior and medial gastrocnemius was performed., Main Outcomes and Measures: Mean EI was calculated for all involved muscle groups. Quantitative EI Sum Scores were calculated as total EI divided by number of muscle groups assessed. We performed a comprehensive literature review to compare our results to previous LOPD muscle ultrasound studies., Results: Six of 20 participants had elevated CK and 15 had ≥ 50% of the most common concerning kinematic physical findings; with normal urine Glc4 in all except one. Based upon muscle EI, the most affected muscles were quadriceps and medial gastrocnemius, with notable elevated EI in thoracic paraspinals. Biceps brachii was the most frequently affected upper extremity muscle. EI sum scores correlated moderately with increasing CK. Statistically significant positive correlation was found between posterior pelvic tilt in sitting and EI of gluteus maximus. Sonographic pattern of muscle involvement was similar to previous studies assessing older patients with LOPD., Conclusions and Relevance: In this study, muscle EI was elevated most often in the quadriceps, tibialis anterior, medial gastrocnemius, thoracic paraspinals, and biceps brachii. Involved muscles generally fit the profile of physical and muscle ultrasound/MRI exam findings in LOPD patients. Muscle ultrasound is recommended for rapid, focused muscle assessment in LOPD, especially those identified via NBS. Future studies should focus on this pattern of ultrasonographic abnormality and changes over time., Competing Interests: None., (© 2023 The Authors.)

Gene therapy with an adeno-associated virus serotype 8 (AAV8) vector (AAV8-LSPhGAA) could eliminate the need for enzyme replacement therapy (ERT) by creating a liver depot for acid α-glucosidase (GAA) production. We report initial safety and bioactivity of the first dose (1.6 × 10 12 vector genomes/kg) cohort (n = 3) in a 52-week open-label, single-dose, dose-escalation study (NCT03533673) in patients with late-onset Pompe disease (LOPD). Subjects discontinued biweekly ERT after week 26 based on the detection of elevated serum GAA activity and the absence of clinically significant declines per protocol. Prednisone (60 mg/day) was administered as immunoprophylaxis through week 4, followed by an 11-week taper. All subjects demonstrated sustained serum GAA activities from 101% to 235% of baseline trough activity 2 weeks following the preceding ERT dose. There were no treatment-related serious adverse events. No subject had anti-capsid T cell responses that decreased transgene expression. Muscle biopsy at week 24 revealed unchanged muscle glycogen content in two of three subjects. At week 52, muscle GAA activity for the cohort was significantly increased (p < 0.05). Overall, these initial data support the safety and bioactivity of AAV8-LSPhGAA, the safety of withdrawing ERT, successful immunoprophylaxis, and justify continued clinical development of AAV8-LSPhGAA therapy in Pompe disease., Competing Interests: Declaration of interests D.D.K. and P.S.K. have developed the technology that is being used in the study. If the technology is commercially successful in the future, the developers and Duke University may benefit financially. D.D.K. has served as a consultant for Sangamo Therapeutics and for Genzyme Sanofi, Amicus, and Vertex; has received grant support from Viking Therapeutics, Genzyme Sanofi, Roivant Rare Diseases, and Amicus; and has equity in Askbio, which is developing gene therapy for Pompe disease. E.C.S. received salary support for his role as PI on this study. S.H. is an employee of Askbio. L.E.C. has received honoraria from Genzyme Sanofi, has participated in research supported by Genzyme Sanofi, Valerion, Biomarin, and by Roivant Sciences; and is a member of the Pompe Registry North American Board of Advisors Genzyme Sanofi. D.B. has received research grant support and travel funds from Genzyme Sanofi, Baebies Inc., Biomarin, Alexion Inc., SOBI biopharma, and JCR biopharma. P.S.K. has received research/grant support from Genzyme Sanofi and Valerion Therapeutics. She received consulting fees and honoraria from Genzyme Sanofi, Amicus Therapeutics, and Vertex. She is a member of the Pompe and Gaucher Disease Registry Advisory Board for Genzyme Sanofi and on the Amicus Scientific advisory board., (Copyright © 2023 The American Society of Gene and Cell Therapy. Published by Elsevier Inc. All rights reserved.)

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Objective: Hypophosphatasia, an inborn error of metabolism characterized by impaired bone mineralization, can affect growth. This study evaluated relationships between anthropometric parameters (height, weight, and body mass index) and clinical manifestations of hypophosphatasia in children., Design: Data from children (aged <18 years) with hypophosphatasia were analyzed from the observational Global Hypophosphatasia Registry., Methods: Anthropometric parameters were evaluated by age group (<2 years and ≥2 years) at assessment. The frequency of hypophosphatasia manifestations was compared between children with short stature (< percentile) and those with normal stature., Results: This analysis included 215 children (54.4% girls). Short stature presented in 16.1% of children aged <2 years and 20.4% of those aged ≥2 years at assessment. Among those with available data (n = 62), height was below the target height (mean: -0.66 standard deviations). Substantial worsening of growth (mean delta height z score: -1.45; delta weight z score: -0.68) occurred before 2 years of age, while in those aged ≥2 years, anthropometric trajectories were maintained (delta height z score: 0.08; delta weight z score: 0.13). Broad-ranging hypophosphatasia manifestations (beyond dental) were observed in most children., Conclusions: Short stature was not a consistent characteristic of children with hypophosphatasia, but growth impairment was observed in those aged <2 years, indicating that hypophosphatasia might affect growth plate activity during infancy. In addition, a broad range of clinical manifestations occurred in those above and below the third percentile for height, suggesting that height alone may not accurately reflect hypophosphatasia disease burden and that weight is less affected than longitudinal growth.

Introduction: Hypophosphatasia (HPP) manifests in adults as fractures/pseudofractures, pain, muscle weakness, and other functional impairments. Better phenotypic disease characterization is needed to help recognize disability and treat patients with HPP., Methods: Baseline/pretreatment demographic, clinical characteristic, and patient-reported disability/health-related quality-of-life (HRQoL) data from adults (≥18 y) in the Global HPP Registry (NCT02306720) were stratified by presence of overt skeletal manifestations (skeletal group) versus muscular/pain manifestations without skeletal manifestations (muscular/pain group) and summarized descriptively. Disability was measured using the Health Assessment Questionnaire-Disability Index (HAQ-DI), and HRQoL using the 36-item Short Form Health Survey (SF-36v2)., Results: Of 468 adults, 300 were classified into the skeletal group and 73 into the muscular/pain group. The skeletal group had a higher median age at baseline (50.1 vs 44.4 y; P =0.047) but a lower median age at first HPP manifestation (12.3 vs 22.1 y; P =0.0473), with more signs and symptoms (median, 4 vs 3; P <0.0001) and involved body systems (median, 3 vs 2; P <0.0001) than the muscular/pain group. More patients in the skeletal group required any use of mobility aids (22.6% vs 3.5%, respectively; P =0.001). Six-Minute Walk test distances walked were similar between groups. SF-36v2 and HAQ-DI scores were similar between groups for physical component summary (n=238; mean [SD]: 40.2 [11.0] vs 43.6 [11.2]; P =0.056), mental component summary (n=238; mean [SD]: 43.6 [11.3] vs 43.8 [11.8]; P =0.902), and HAQ-DI (n=239; median [minimum, maximum]: 0.4 [0.0, 2.7] vs 0.3 [0.0, 2.1]; P =0.22)., Conclusion: Adults with HPP experience similar QoL impairment regardless of skeletal involvement., Registration: https://clinicaltrials.gov/ct2/show/NCT02306720 and https://www.encepp.eu/encepp/viewResource.htm?id=47907, identifier NCT02306720; EUPAS13514., Competing Interests: Authors AP and SM are employed by Alexion, AstraZeneca Rare Disease. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declare that this study received funding from Alexion, AstraZeneca Rare Disease. The funder had the following involvement in the study: conception and design of the Registry, collection of data, and statistical analyses, as described in the Author Contributions section., (Copyright © 2023 Dahir, Kishnani, Martos-Moreno, Linglart, Petryk, Rockman-Greenberg, Martel, Ozono, Högler and Seefried.)

Purpose: Mini-COMET (NCT03019406; Sanofi) is a phase 2, open-label, ascending-dose, 3-cohort study, evaluating avalglucosidase alfa safety, pharmacokinetics, and efficacy in individuals with infantile-onset Pompe disease aged <18 years who previously received alglucosidase alfa and showed clinical decline (cohorts 1 and 2) or suboptimal response (cohort 3)., Methods: During a 25-week primary analysis period, cohorts 1 and 2 received avalglucosidase alfa 20 and 40 mg/kg every other week, respectively, for 6 months, whereas cohort 3 individuals were randomized (1:1) to receive avalglucosidase alfa 40 mg/kg every other week or alglucosidase alfa (current stable dose) for 6 months., Results: In total, 22 individuals were enrolled (cohort 1 [n = 6], cohort 2 [n = 5], cohort 3-avalglucosidase alfa [n = 5], and cohort 3-alglucosidase alfa [n = 6]). Median treatment compliance was 100%. None of the individuals discontinued treatment or died. Percentages of individuals with treatment-emergent adverse events were similar across dose and treatment groups. No serious or severe treatment-related treatment-emergent adverse events occurred. Trends for better motor function from baseline to week 25 were observed for 40 mg/kg every other week avalglucosidase alfa compared with either 20 mg/kg every other week avalglucosidase alfa or alglucosidase alfa up to 40 mg/kg weekly., Conclusion: These data support the positive clinical effect of avalglucosidase alfa in patients with infantile-onset Pompe disease previously declining on alglucosidase alfa., Competing Interests: Conflict of Interest P.S.K. reports advisory board participation for Amicus Therapeutics, Baebies, and Sanofi; receiving consulting fees from Amicus Therapeutics, Asklepios Biopharmaceutical Inc (AskBio), JCR Pharma Co Ltd, Maze Therapeutics, and Sanofi; performing contracted research for Amicus Therapeutics and Sanofi; receiving honoraria from Amicus Therapeutics, AskBio, Maze Therapeutics, and Sanofi; having ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in AskBio and Maze Therapeutics; and receiving travel expenses from Amicus Therapeutics and Sanofi. D.K. reports advisory board participation for AskBio and Sanofi; performing contracted research for Sanofi; serving on the Speaker’s bureau for Sanofi; and receiving travel expenses from AskBio and Sanofi. A.Bra. reports advisory board participation for Alexion, Sanofi, and Shire; receiving consulting fees from Alexion; and receiving travel expenses from Alexion, BioMarin, Orphan Europe, Sanofi, and Shire. A.Bro. reports advisory board participation for Sanofi and receiving honoraria from Orchard Therapeutics and Sanofi. J.D. reports advisory board participation for Sanofi, Recordati RRD, and Orchard Therapeutics; receiving consulting fees from bluebird bio Inc; and serving on the Speaker’s bureau for Sanofi, Recordati RRD, and FYMCA Medical Ltd. S.H.H. reports advisory board participation for Alexion Pharmaceutical Inc; performing contracted research for Sanofi; receiving honoraria from Alexion Pharmaceutical Inc; membership of the Seattle Children’s Hospital workforce; serving as temporary CEO of KEY PROTEO, Inc; being an inventor of intellectual property that has been licensed to KEY PROTEO, Inc; being a founder of KEY PROTEO, Inc and having ownership equity interests in the company; and receiving royalties from UpToDate. S.K., F.L., and H.O. declare no conflicts of interest. S.P. reports receiving travel expenses from Sanofi. S.G.P. reports performing contracted research for Sanofi and receiving consulting fees from Sanofi. K.A.H. and her spouse are employees of Sanofi and both have ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in Sanofi. B.K. is an employee of Sanofi and has ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in Sanofi. X.M. is an employee of TechData Service LLC (contracted to Sanofi). S.S. is an employee of Sanofi and has ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in Sanofi. C.W. reports receiving consulting fees from Sanofi and Regenxbio. A.Z. is an employee of Sanofi and has ownership interest of <5% (stocks, stock options, or other ownership interest excluding diversified mutual funds) in Sanofi Canada. Y.-H.C. reports advisory board participation for Amicus Therapeutics and Sanofi; receiving consulting fees from Amicus Therapeutics and Sanofi; performing contracted research for Sanofi; and receiving honoraria from Biogen, Novartis, Sanofi, and Takeda., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Glycogen debranching enzyme deficiency in glycogen storage disease type III (GSD III) results in excessive glycogen accumulation in multiple tissues, primarily the liver, heart, and skeletal muscle. We recently reported that an adeno-associated virus vector expressing a bacterial debranching enzyme (pullulanase) driven by the ubiquitous CMV enhancer/chicken β-actin (CB) promoter cleared glycogen in major affected tissues of infant GSD IIIa mice. In this study, we developed a potentially novel dual promoter consisting of a liver-specific promoter (LSP) and the CB promoter for gene therapy in adult GSD IIIa mice. Ten-week treatment with an adeno-associated virus vector containing the LSP-CB dual promoter in adult GSD IIIa mice significantly increased pullulanase expression and reduced glycogen contents in the liver, heart, and skeletal muscle, accompanied by the reversal of liver fibrosis, improved muscle function, and a significant decrease in plasma biomarkers alanine aminotransferase, aspartate aminotransferase, and creatine kinase. Compared with the CB promoter, the dual promoter effectively decreased pullulanase-induced cytotoxic T lymphocyte responses and enabled persistent therapeutic gene expression in adult GSD IIIa mice. Future studies are needed to determine the long-term durability of dual promoter-mediated expression of pullulanase in adult GSD IIIa mice and in large animal models.

Purpose: The addition of Pompe disease (Glycogen Storage Disease Type II) to the Recommended Uniform Screening Panel in the United States has led to an increase in the number of variants of uncertain significance (VUS) and novel variants identified in the GAA gene. This presents a diagnostic challenge, especially in the setting of late-onset Pompe disease when symptoms are rarely apparent at birth. There is an unmet need for validated functional studies to aid in classification of GAA variants. Methods: We developed an in vitro mammalian cell expression and functional analysis system based on guidelines established by the Clinical Genome Resource (ClinGen) Sequence Variant Interpretation Working Group for PS3/BS3. We validated the assay with 12 control variants and subsequently analyzed eight VUS or novel variants in GAA identified in patients with a positive newborn screen for Pompe disease without phenotypic evidence of infantile-onset disease. Results: The control variants were analyzed in our expression system and an activity range was established. The pathogenic controls had GAA activity between 0% and 11% of normal. The benign or likely benign controls had an activity range of 54%-100%. The pseudodeficiency variant had activity of 17%. These ranges were then applied to the variants selected for functional studies. Using the threshold of <11%, we were able to apply PS3&#95; supporting to classify two variants as likely pathogenic (c.316C > T and c.1103G > A) and provide further evidence to support the classification of likely pathogenic for two variants (c.1721T > C and c.1048G > A). One variant (c.1123C > T) was able to be reclassified based on other supporting evidence. We were unable to reclassify three variants (c.664G > A, c.2450A > G, and c.1378G > A) due to insufficient or conflicting evidence. Conclusion: We investigated eight GAA variants as proof of concept using our validated and reproducible in vitro expression and functional analysis system. While additional work is needed to further refine our system with additional controls and different variant types in order to apply the PS3/BS3 criteria at a higher level, this tool can be utilized for variant classification to meet the growing need for novel GAA variant classification in the era of newborn screening for Pompe disease., Competing Interests: CR has received consulting fees and honoraria from Amicus Therapeutics, Inc. and serves as co-chair of the ClinGen Lysosomal Storage Disorders Variant Curation Expert Panel. DB has received consulting fees and honoraria from Amicus Therapeutics, Inc. PK has received research/grant support from Sanofi Genzyme and Amicus Therapeutics, Inc. PK has received consulting fees and honoraria from Sanofi Genzyme, Amicus Therapeutics, Inc., Maze Therapeutics, JCR Pharmaceutical and Asklepios Biopharmaceutical, Inc. (AskBio). PK is a member of the Pompe and Gaucher Disease Registry Advisory Board for Sanofi Genzyme, Amicus Therapeutics, and Baebies. PK has equity in Asklepios Biopharmaceutical, Inc. (AskBio), which is developing gene therapy for Pompe disease and Maze Therapeutics, which is developing small molecule in Pompe disease. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Goomber, Huggins, Rehder, Cohen, Bali and Kishnani.)

Background: The clinical signs and symptoms of hypophosphatasia (HPP) can manifest during any stage of life. The age at which a patient's symptoms are reported can impact access to targeted treatment with enzyme replacement therapy (asfotase alfa), as this treatment is indicated for patients with pediatric-onset HPP in most countries. As such, many patients reported to have adult-onset HPP typically do not receive treatment. Comparison of the disease in treated and untreated adult patients is confounded by the approved indication. To avoid this confounding factor, a comparison between baseline disease manifestations prominent among treated versus untreated adult patients was limited to those with pediatric-onset HPP using data collected from the Global HPP Registry. The hypothesis was that treated adults will have a greater disease burden at baseline than untreated adults. The analysis of disease manifestations in adults with adult-onset HPP was conducted separately., Results: A total of 398 adults with HPP were included; 213 with pediatric-onset (114 treated, 99 untreated) and 141 with adult-onset HPP (2 treated and 139 untreated). The treated, pediatric-onset patients were more likely to have a history of pain (prevalence ratio [PR]: 1.3, 95% confidence interval [CI] 1.1, 1.4), skeletal (PR: 1.3, 95% CI 1.1, 1.6), constitutional/metabolic (PR: 1.7, 95% CI 1.3, 2.0), muscular (PR: 1.8, 95% CI 1.4, 2.1) and neurological (PR: 1.7, 95% CI 1.1, 2.3) manifestations of HPP, and also had poorer measures for health-related quality of life, pain, and disability compared with untreated pediatric-onset patients. In patients with adult-onset HPP, the most frequent signs and symptoms were chronic bone pain (52.5%), dental manifestations (42.6%), fatigue (23.4%), recurrent fractures or pseudofractures (22.0%), and generalized body pain (22.0%)., Conclusions: Along with the more classical skeletal signs and symptoms, pain, muscular, and constitutional/metabolic manifestations are common in adults with HPP, regardless of age of disease onset, highlighting a full spectrum of HPP manifestations., (© 2022. The Author(s).)

Infantile onset Pompe disease (IOPD) is a rare devastating disease that presents in early infancy with rapidly progressive hypertrophic cardiomyopathy, severe generalized myopathy and death within the first year of life. The emergence of enzyme replacement therapy (ERT) with recombinant human acid alpha glucosidase (rhGAA) has improved the natural course of IOPD with a significant impact on cardiomyopathy but has a more limited effect on the progression of myopathy and consequently the later deterioration of the disease. Possible reasons for reduced ERT efficacy include insufficient enzyme, partial targeting of skeletal muscle and the development of IgG rhGAA antibodies especially in patients who are cross-reactive immunological material (CRIM) negative. We report a CRIM-negative IOPD female patient who started treatment upon diagnosis at 4.5 months with ERT at 20 mg/kg every other week and a course of combined immunomodulation with rituximab, methotrexate and IVIG according to the published Duke protocol and increased ERT within a month to 40 mg/kg/week. Despite initial good clinical response to ERT and immunomodulation, monthly monitoring identified a gradual increase of serum antibody titers to rhGAA necessitating a second course of immunomodulation with bortezomib and maintenance rituximab and methotrexate. A gradual reduction in frequency of immunotherapy was instituted and over a period of 14 months was discontinued. Serum anti-rhGAA antibody titers remained negative for 5 months since cessation of immunomodulation and the patient is now immune tolerant with recovery of CD19. At the age of 30 months the patient is walking independently and has normal cardiac function and anatomy. We recommend initiating ERT at 40 mg/kg/week in CRIM-negative IOPD patients, concomitant with immunomodulation and monthly monitoring of serum anti-rhGAA IgG titers upon confirmation of the diagnosis., Competing Interests: AKD has received grant support from Sanofi Genzyme and the Lysosomal Disease Network. PSK has received research/grant support from Sanofi Genzyme and Amicus Therapeutics. PSK has received consulting fees and honoraria from Sanofi Genzyme, Amicus Therapeutics, Maze Therapeutics, JCR Pharmaceutical and Asklepios Biopharmaceutical, Inc. (AskBio). PSK is a member of the Pompe and Gaucher Disease Registry Advisory Board for Sanofi Genzyme, Amicus Therapeutics, and Baebies. PSK has equity in Asklepios Biopharmaceutical, Inc. (AskBio), which is developing gene therapy for Pompe disease and Maze Therapeutics, which is developing small molecule in Pompe disease. YZ has received travel reimbursement from Sanofi Genzyme, RS has received travel reimbursement and speaker payments from Sanofi Genzyme., (© 2022 The Authors.)

Introduction: Biotinidase synthesis is needed to recycle biotin for essential metabolic reactions. Biotinidase activity is lower than normal levels in advanced liver disease but is higher in hepatic glycogen storage disorders (GSDs), however the cause of this association remains unclear., Methods: In this study, biotinidase activity was measured in plasma samples from 45 individuals with hepatic GSDs; GSDI (a, b; n = 25) and GSD III (a, b; n = 20), complemented by a chart review to associate biotinidase activity levels with clinical laboratory and imaging findings known to be implicated in these GSDs., Results: Our findings showed variation in biotinidase activity levels among subjects with GSD I and III; biotinidase activity correlated positively with hypertriglyceridemia in subjects with GSD I ( r  = 0.47, P = 0.036) and GSD III ( r  = 0.58, P = 0.014), and correlated negatively with age ( r  = -0.50, P = 0.03) in patients with GSD III. Additionally, biotinidase activity was reduced, albeit within the normal range in subjects with evidence of fibrosis/cirrhosis, as compared to subjects with hepatomegaly with or without steatosis (P = 0.002)., Discussions: These findings suggest that abnormal lipid metabolism in GSD I and III and progressive liver disease in GSD III may influence biotinidase activity levels. We suggest that a prospective, multi-center, longitudinal study designed to assess the significance of monitoring biotinidase activity in a larger cohort with hepatic GSDs is warranted to confirm this observation., Take-Home Message: Altered lipid metabolism and advancing liver fibrosis/cirrhosis may influence biotinidase activity levels in patients with hepatic glycogen storage disease. Thus, longitudinal monitoring of biotinidase activity, when combined with clinical and other biochemical findings may be informative., Competing Interests: The authors declare no conflicts of interest., (© 2022 The Authors.)

Background: There are currently no pharmacological therapies to address the intellectual disability associated with Down syndrome. Excitatory/inhibitory imbalance has been hypothesized to contribute to impairments in cognitive functioning in Down syndrome. Negative modulation of the GABA A -α5 receptor is proposed as a mechanism to attenuate GABAergic function and restore the excitatory/inhibitory balance., Methods: Basmisanil, a selective GABA A -α5 negative allosteric modulator, was evaluated at 120 mg or 240 mg BID (80 or 160 mg for 12-13 years) in a 6-month, randomized, double-blind, placebo-controlled phase II trial (Clematis) for efficacy and safety in adolescents and young adults with Down syndrome. The primary endpoint was based on a composite analysis of working memory (Repeatable Battery for the Assessment of Neuropsychological Scale [RBANS]) and independent functioning and adaptive behavior (Vineland Adaptive Behavior Scales [VABS-II] or the Clinical Global Impression-Improvement [CGI-I]). Secondary measures included the Behavior Rating Inventory of Executive Functioning-Preschool (BRIEF-P), Clinical Evaluation of Language Fundamentals (CELF-4), and Pediatric Quality of Life Inventory (Peds-QL). EEG was conducted for safety monitoring and quantitatively analyzed in adolescents., Results: Basmisanil was safe and well-tolerated; the frequency and nature of adverse events were similar in basmisanil and placebo arms. EEG revealed treatment-related changes in spectral power (increase in low ~ 4-Hz and decrease in high ~ 20-Hz frequencies) providing evidence of functional target engagement. All treatment arms had a similar proportion of participants showing above-threshold improvement on the primary composite endpoint, evaluating concomitant responses in cognition and independent functioning (29% in placebo, 20% in low dose, and 25% in high dose). Further analysis of the individual measures contributing to the primary endpoint revealed no difference between placebo and basmisanil-treated groups in either adolescents or adults. There were also no differences across the secondary endpoints assessing changes in executive function, language, or quality of life., Conclusions: Basmisanil did not meet the primary efficacy objective of concomitant improvement on cognition and adaptive functioning after 6 months of treatment, despite evidence for target engagement. This study provides key learnings for future clinical trials in Down syndrome., Trial Registration: The study was registered on December 31, 2013, at clinicaltrials.gov as NCT02024789., (© 2022. The Author(s).)

Introduction: A deficiency of glycogen debrancher enzyme in patients with glycogen storage disease type III (GSD III) manifests with hepatic, cardiac, and muscle involvement in the most common subtype (type a), or with only hepatic involvement in patients with GSD IIIb., Objective and Methods: To describe longitudinal biochemical, radiological, muscle strength and ambulation, liver histopathological findings, and clinical outcomes in adults (≥18 years) with glycogen storage disease type III, by a retrospective review of medical records., Results: Twenty-one adults with GSD IIIa (14 F & 7 M) and four with GSD IIIb (1 F & 3 M) were included in this natural history study. At the most recent visit, the median (range) age and follow-up time were 36 (19-68) and 16 years (0-41), respectively. For the entire cohort: 40% had documented hypoglycemic episodes in adulthood; hepatomegaly and cirrhosis were the most common radiological findings; and 28% developed decompensated liver disease and portal hypertension, the latter being more prevalent in older patients. In the GSD IIIa group, muscle weakness was a major feature, noted in 89% of the GSD IIIa cohort, a third of whom depended on a wheelchair or an assistive walking device. Older individuals tended to show more severe muscle weakness and mobility limitations, compared with younger adults. Asymptomatic left ventricular hypertrophy (LVH) was the most common cardiac manifestation, present in 43%. Symptomatic cardiomyopathy and reduced ejection fraction was evident in 10%. Finally, a urinary biomarker of glycogen storage (Glc 4 ) was significantly associated with AST, ALT and CK., Conclusion: GSD III is a multisystem disorder in which a multidisciplinary approach with regular clinical, biochemical, radiological and functional (physical therapy assessment) follow-up is required. Despite dietary modification, hepatic and myopathic disease progression is evident in adults, with muscle weakness as the major cause of morbidity. Consequently, definitive therapies that address the underlying cause of the disease to correct both liver and muscle are needed., (© 2021 The Authors. Published by Elsevier Inc.)

Pompe disease (PD) is a glycogen storage disorder caused by deficient activity of acid alpha-glucosidase (GAA). We sought to review the latest available evidence on the safety and efficacy of recombinant human GAA enzyme replacement therapy (ERT) for late-onset PD (LOPD)., Methods: We systematically searched the MEDLINE (via PubMed), Embase, and Cochrane databases for prospective clinical studies evaluating ERT for LOPD on pre-specified outcomes. A meta-analysis was also performed., Results: Of 1601 articles identified, 22 were included. Studies were heterogeneous and with very low certainty of evidence for most outcomes. The following outcomes showed improvements associated with GAA ERT, over a mean follow-up of 32.5 months: distance walked in the 6-min walking test (6MWT) (mean change 35.7 m (95% confidence interval [CI] 7.78, 63.75)), physical domain of the SF-36 quality of life (QOL) questionnaire (mean change 1.96 (95% CI 0.33, 3.59)), and time on ventilation (TOV) (mean change -2.64 h (95% CI -5.28, 0.00)). There were no differences between the pre- and post-ERT period for functional vital capacity (FVC), Walton and Gardner-Medwin Scale score, upper-limb strength, or total SF-36 QOL score. Adverse events (AEs) after ERT were mild in most cases., Conclusion: Considering the limitations imposed by the rarity of PD, our data suggest that GAA ERT improves 6MWT, physical QOL, and TOV in LOPD patients. ERT was safe in the studied population. PROSPERO register: 135102.

Bulbar and respiratory weakness occur commonly in children with Pompe disease and frequently lead to dysarthria. However, changes in vocal quality associated with this motor speech disorder are poorly described. The goal of this study was to characterize the vocal function of children with Pompe disease using auditory-perceptual and physiologic/acoustic methods. High-quality voice recordings were collected from 21 children with Pompe disease. The Grade, Roughness, Breathiness, Asthenia, and Strain (GRBAS) scale was used to assess voice quality and ratings were compared to physiologic/acoustic measurements collected during sustained phonation tasks, reading of a standard passage, and repetition of a short phrase at maximal volume. Based on ratings of grade, dysphonia was present in 90% of participants and was most commonly rated as mild or moderate in severity. Duration of sustained phonation tasks was reduced and shimmer was increased in comparison to published reference values for children without dysphonia. Specific measures of loudness were found to have statistically significant relationships with perceptual ratings of grade, breathiness, asthenia, and strain. Our data suggest that dysphonia is common in children with Pompe disease and primarily reflects impairments in respiratory and laryngeal function; however, the primary cause of dysphonia remains unclear. Future studies should seek to quantify the relative contribution of deficits in individual speech subsystems on voice quality and motor speech performance more broadly.

Despite widespread clinical genetic testing, many individuals with suspected genetic conditions lack a precise diagnosis, limiting their opportunity to take advantage of state-of-the-art treatments. In some cases, testing reveals difficult-to-evaluate structural differences, candidate variants that do not fully explain the phenotype, single pathogenic variants in recessive disorders, or no variants in genes of interest. Thus, there is a need for better tools to identify a precise genetic diagnosis in individuals when conventional testing approaches have been exhausted. We performed targeted long-read sequencing (T-LRS) using adaptive sampling on the Oxford Nanopore platform on 40 individuals, 10 of whom lacked a complete molecular diagnosis. We computationally targeted up to 151 Mbp of sequence per individual and searched for pathogenic substitutions, structural variants, and methylation differences using a single data source. We detected all genomic aberrations-including single-nucleotide variants, copy number changes, repeat expansions, and methylation differences-identified by prior clinical testing. In 8/8 individuals with complex structural rearrangements, T-LRS enabled more precise resolution of the mutation, leading to changes in clinical management in one case. In ten individuals with suspected Mendelian conditions lacking a precise genetic diagnosis, T-LRS identified pathogenic or likely pathogenic variants in six and variants of uncertain significance in two others. T-LRS accurately identifies pathogenic structural variants, resolves complex rearrangements, and identifies Mendelian variants not detected by other technologies. T-LRS represents an efficient and cost-effective strategy to evaluate high-priority genes and regions or complex clinical testing results., (Copyright © 2021 American Society of Human Genetics. Published by Elsevier Inc. All rights reserved.)

Recent advances in next-genetic sequencing technology have facilitated an expansion in the use of exome and genome sequencing in the research and clinical settings. While this has aided in the genetic diagnosis of individuals with atypical clinical presentations, there has been a marked increase in the number of incidentally identified variants of uncertain diagnostic significance in genes identified as clinically actionable by the American College of Medical Genetics guidelines. Approximately 20 of these genes are associated with cardiac diseases, which carry a significant risk of sudden cardiac death. While identification of at-risk individuals is paramount, increased discovery of incidental variants of uncertain diagnostic significance has placed a burden on the clinician tasked with determining the diagnostic significance of these findings. Herein, we describe the scope of this emerging problem using cardiovascular genetics to illustrate the challenges associated with variants of uncertain diagnostic significance interpretation. We review the evidence for diagnostic weight of these variants, discuss the role of clinical genetics providers in patient care, and put forward general recommendations about the interpretation of incidentally identified variants found with clinical genetic testing.

Background: There are new emerging phenotypes in Pompe disease, and studies on smooth muscle pathology are limited. Gastrointestinal (GI) manifestations are poorly understood and underreported in Pompe disease., Methods: To understand the extent and the effects of enzyme replacement therapy (ERT; alglucosidase alfa) in Pompe disease, we studied the histopathology (entire GI tract) in Pompe mice (GAAKO 6 neo /6 neo ). To determine the disease burden in patients with late-onset Pompe disease (LOPD), we used Patient-Reported Outcomes Measurements Information System (PROMIS)-GI symptom scales and a GI-focused medical history., Results: Pompe mice showed early, extensive, and progressive glycogen accumulation throughout the GI tract. Long-term ERT (6 months) was more effective to clear the glycogen accumulation than short-term ERT (5 weeks). GI manifestations were highly prevalent and severe, presented early in life, and were not fully amenable to ERT in patients with LOPD ( n = 58; age range: 18-79 years, median age: 51.55 years; 35 females; 53 on ERT)., Conclusion: GI manifestations cause a significant disease burden on adults with LOPD, and should be evaluated during routine clinical visits, using quantitative tools (PROMIS-GI measures). The study also highlights the need for next generation therapies for Pompe disease that target the smooth muscles.

Background/objectives: Late-onset Pompe disease (LOPD) is slowly progressive, making it difficult to assess clinical change and response to interventions. In this study, quantitative muscle ultrasonography (QMUS) and electrical impedance myography (EIM) were evaluated as potential biomarkers., Methods: 25 patients with confirmed LOPD were recruited from the Duke Pompe Clinic and evaluated with standard clinical measures, QMUS, standard EIM (sEIM) and hand-held EIM (hEIM). Patients were evaluated at baseline, 12 months and 24 months. MUS, sEIM and hEIM were compared with the clinical data. Five patients were given hEIM devices to perform measurements at home., Results: QMUS and hEIM had good reliability as measures of muscle structure and conduction properties. Home, patient-performed hEIM measurements did not differ significantly from those performed in the clinic setting. Thirteen patients completed all follow-up measures. Most measures did not change over the study period, however, vastus lateralis echointensity increased 27%, a sign of declining muscle health. Additionally, significant correlations between QMUS, hEIM and measures of muscle strength and function were present., Conclusions: QMUS and hEIM may provide useful outcome measures for future studies in LOPD with hEIM providing an opportunity to collect data at home. Larger, multicenter studies are needed to explore these possibilities., (© 2021 The Authors. Published by Elsevier Inc.)

Infantile-onset Pompe disease (IOPD) is a glycogen storage disease caused by a deficiency of acid alpha-glucosidase (GAA). Treatment with recombinant human GAA (rhGAA, alglucosidase alfa) enzyme replacement therapy (ERT) significantly improves clinical outcomes; however, many IOPD children treated with rhGAA develop anti-drug antibodies (ADA) that render the therapy ineffective. Antibodies to rhGAA are driven by T cell responses to sequences in rhGAA that differ from the individuals' native GAA (nGAA). The goal of this study was to develop a tool for personalized immunogenicity risk assessment (PIMA) that quantifies T cell epitopes that differ between nGAA and rhGAA using information about an individual's native GAA gene and their HLA DR haplotype, and to use this information to predict the risk of developing ADA. Four versions of PIMA have been developed. They use EpiMatrix, a computational tool for T cell epitope identification, combined with an HLA-restricted epitope-specific scoring feature (iTEM), to assess ADA risk. One version of PIMA also integrates JanusMatrix, a Treg epitope prediction tool to identify putative immunomodulatory (regulatory) T cell epitopes in self-proteins. Using the JanusMatrix-adjusted version of PIMA in a logistic regression model with data from 48 cross-reactive immunological material (CRIM)-positive IOPD subjects, those with scores greater than 10 were 4-fold more likely to develop ADA (p<0.03) than those that had scores less than 10. We also confirmed the hypothesis that some GAA epitopes are immunomodulatory. Twenty-one epitopes were tested, of which four were determined to have an immunomodulatory effect on T effector response in vitro . The implementation of PIMA V3J on a secure-access website would allow clinicians to input the individual HLA DR haplotype of their IOPD patient and the GAA pathogenic variants associated with each GAA allele to calculate the patient's relative risk of developing ADA, enhancing clinical decision-making prior to initiating treatment with ERT. A better understanding of immunogenicity risk will allow the implementation of targeted immunomodulatory approaches in ERT-naïve settings, especially in CRIM-positive patients, which may in turn improve the overall clinical outcomes by minimizing the development of ADA. The PIMA approach may also be useful for other types of enzyme or factor replacement therapies., Competing Interests: ADG and WDM are senior officers and shareholders, and SM, FET, SK, MA, and SL are employees of EpiVax, Inc., a company specializing in immunoinformatic analysis. EpiVax, Inc. own patents to technologies utilized by associated authors in the research reported here. AKD has received grant support from Sanofi Genzyme and the lysosomal disease network. PSK has received research/grant support from Sanofi Genzyme, Valerion Therapeutics, and Amicus Therapeutics. PSK has received consulting fees and honoraria from Sanofi Genzyme, Amicus Therapeutics, Maze Therapeutics, JCR Pharmaceutical and Asklepios Biopharmaceutical, Inc. (AskBio). PSK is a member of the Pompe and Gaucher Disease Registry Advisory Board for Sanofi Genzyme, Amicus Therapeutics, and Baebies. PSK has equity in Asklepios Biopharmaceutical, Inc. (AskBio), which is developing gene therapy for Pompe disease and Maze Therapeutics, which is developing small molecule in Pompe disease. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 De Groot, Desai, Lelias, Miah, Terry, Khan, Li, Yi, Ardito, Martin and Kishnani.)

In Pompe disease, the deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA) causes skeletal and cardiac muscle weakness, respiratory failure, and premature death. While enzyme replacement therapy using recombinant human GAA (rhGAA) can significantly improve patient outcomes, detailed disease mechanisms and incomplete therapeutic effects require further studies. Here we report a three-dimensional primary human skeletal muscle ("myobundle") model of infantile-onset Pompe disease (IOPD) that recapitulates hallmark pathological features including reduced GAA enzyme activity, elevated glycogen content and lysosome abundance, and increased sensitivity of muscle contractile function to metabolic stress. In vitro treatment of IOPD myobundles with rhGAA or adeno-associated virus (AAV)-mediated hGAA expression yields increased GAA activity and robust glycogen clearance, but no improvements in stress-induced functional deficits. We also apply RNA sequencing analysis to the quadriceps of untreated and AAV-treated GAA -/- mice and wild-type controls to establish a Pompe disease-specific transcriptional signature and reveal novel disease pathways. The mouse-derived signature is enriched in the transcriptomic profile of IOPD vs. healthy myobundles and partially reversed by in vitro rhGAA treatment, further confirming the utility of the human myobundle model for studies of Pompe disease and therapy.

Purpose: To assess the magnitude of benefit to early treatment initiation, enabled by newborn screening or prenatal diagnosis, in patients with cross-reactive immunological material (CRIM)-negative infantile Pompe disease (IPD), treated with enzyme replacement therapy (ERT) and prophylactic immune tolerance induction (ITI) with rituximab, methotrexate, and intravenous immunoglobulin (IVIG)., Methods: A total of 41 CRIM-negative IPD patients were evaluated. Among patients who were treated with ERT + ITI (n = 30), those who were invasive ventilator-free at baseline and had ≥6 months of follow-up were stratified based on age at treatment initiation: (1) early (≤4 weeks), (2) intermediate (>4 and ≤15 weeks), and (3) late (>15 weeks). A historical cohort of 11 CRIM-negative patients with IPD treated with ERT monotherapy served as an additional comparator group., Results: Twenty patients were included; five, seven, and eight in early, intermediate, and late treatment groups, respectively. Genotypes were similar across the three groups. Early-treated patients showed significant improvements in left ventricular mass index, motor and pulmonary outcomes, as well as biomarkers creatine kinase and urinary glucose tetrasaccharide, compared with those treated later., Conclusion: Our preliminary data suggest that early treatment with ERT + ITI can transform the long-term CRIM-negative IPD phenotype, which represents the most severe end of the Pompe disease spectrum.