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Propionic Acidemia (PROP) is an inherited metabolic disorder, with defect in the enzyme propionyl-CoA carboxylase (PCC) which catalyzes catabolism of two of the branched-chain amino acids (BCAA), valine, isoleucine. Nutritional management in PROP depends on dietary protein restriction and consumption of medical formula depleted of the offending amino acids. Recently, concerns have been raised about medical formula due to imbalanced content of BCAA (high leucine - another BCAA, and no valine/isoleucine), which negatively impacts plasma concentrations of BCAA, and growth in children with PROP.To determine an optimal BCAA ratio at which total body protein synthesis is optimized in healthy children using the indicator amino acid oxidation method (oxidation of L-A total of 8 healthy children were studied, completing 42 study days. Significant differences in FBCAA ratio of 1:0:0, present in medical formula limited total body protein synthesis. A balanced BCAA ratio was found between 1:0.26:0.28 and 1:0.35:0.4 (leucine:isoleucine:valine). Future research is needed to test this optimal BCAA ratio for optimizing protein synthesis in patients with PROP.The article describes a proof-of-concept study done on healthy school-aged children testing different ratios of branched chain amino acid (BCAA, leucine:isoleucine:valine), in order to determine an optimal ratio at which total body protein synthesis is improved and has implications for dietary management of children with Propionic Acidemia (PROP).

Background Propionic acidemia (PROP) is an autosomal recessive inherited deficiency of propionyl‐CoA carboxylase (PCC) which is involved in the catalytic breakdown of the amino acids valine, isoleucine, methionine, and threonine. PROP nutritional management is based on dietary protein restriction and use of special medical formulas which are free of the offending amino acids, but are enriched in leucine. The resulting imbalance among branched‐chain amino acids negatively impacts plasma concentrations of valine and isoleucine, which might impact growth in children with PROP. Objective and Methods Our primary objective was to describe dietary protein and calorie intake and their impact on long‐term growth outcomes of four PROP patients. This was accomplished through a longitudinal retrospective chart review following the cohort from birth to 18 years. Results All children (n = 4) had poor growth outcomes with persistently reduced height‐for‐age Z scores, and elevated weight and body mass index (BMI) Z scores. Energy intakes for all subjects were within 80% to 120% of the dietary reference intakes for age. All children had low intakes of intact protein compared with current guidelines and were supplemented with medical formula and single l‐amino acids (valine and/or isoleucine), which led to the excess consumption of total protein. Conclusion Despite adequate total protein and energy intakes, all children had persistently low height Z scores. Restricted intact protein consumption together with the abundant use of medical formula could have affected overall growth. To optimize dietary management in patients with PROP, further research is needed to determine the optimal intake of medical formula relative to intact protein.

BackgroundThe Treatable ID App was created in 2012 as digital tool to improve early recognition and intervention for treatable inherited metabolic disorders (IMDs) presenting with global developmental delay and intellectual disability (collectively ‘treatable IDs’). Our aim is to update the 2012 review on treatable IDs and App to capture the advances made in the identification of new IMDs along with increased pathophysiological insights catalyzing therapeutic development and implementation.MethodsTwo independent reviewers queried PubMed, OMIM and Orphanet databases to reassess all previously included disorders and therapies and to identify all reports on Treatable IDs published between 2012 and 2021. These were included if listed in the International Classification of IMDs (ICIMD) and presenting with ID as a major feature, and if published evidence for a therapeutic intervention improving ID primary and/or secondary outcomes is available. Data on clinical symptoms, diagnostic testing, treatment strategies, effects on outcomes, and evidence levels were extracted and evaluated by the reviewers and external experts. The generated knowledge was translated into a diagnostic algorithm and updated version of the App with novel features.ResultsOur review identified 116 treatable IDs (139 genes), of which 44 newly identified, belonging to 17 ICIMD categories. The most frequent therapeutic interventions were nutritional, pharmacological and vitamin and trace element supplementation. Evidence level varied from 1 to 3 (trials, cohort studies, case–control studies) for 19% and 4–5 (case-report, expert opinion) for 81% of treatments. Reported effects included improvement of clinical deterioration in 62%, neurological manifestations in 47% and development in 37%.ConclusionThe number of treatable IDs identified by our literature review increased by more than one-third in eight years. Although there has been much attention to gene-based and enzyme replacement therapy, the majority of effective treatments are nutritional, which are relatively affordable, widely available and (often) surprisingly effective. We present a diagnostic algorithm (adjustable to local resources and expertise) and the updated App to facilitate a swift and accurate workup, prioritizing treatable IDs. Our digital tool is freely available as Native and Web App (www.treatable-id.org) with several novel features. Our Treatable ID endeavor contributes to the Treatabolome and International Rare Diseases Research Consortium goals, enabling clinicians to deliver rapid evidence-based interventions to our rare disease patients.

Background Morquio B disease (MBD) is a distinct GLB1‐related dysostosis multiplex presenting a mild phenocopy of GALNS‐related Morquio A disease. Previously reported cases from European countries carry the W273L variant on at least one GLB1 allele and exhibit a pure skeletal phenotype (pure MBD). Only a minority of MBD cases have been described with additional neuronopathic findings (MBD plus). Objectives and Methods With the aim to further describe patterns of MBD‐related dysostosis multiplex, we analyzed clinical, biochemical, and genetic features in 17 cases with GLB1‐related dysostosis multiplex living and diagnosed in Brazil. Results About 14 of the 17 individuals had three or more skeletal findings characteristic of Morquio syndrome. Two had no additional neuronopathic features (pure MBD) and 12 exhibited additional neuronopathic features (MBD plus). Three of the 17 cases had mild dysostosis without distinct features of MBD. Seven of the 12 MBD plus patients had signs of spinal cord compression (SCC), as a result of progressive spinal vertebral dysostosis. There was an age‐dependent increase in the number of skeletal findings and in the severity of growth impairment. GLB1 mutation analysis was completed in 10 of the 14 MBD patients. T500A occurred in compound heterozygosity in 8 of the 19 alleles. Conclusion Our study extends the phenotypic spectrum of GLB1‐related conditions by describing a cohort of patients with MBD and GM1‐gangliosidosis (MBD plus). Targeting the progressive nature of the skeletal manifestations in the development of new therapies for GLB1‐related conditions is warranted.

Background KRAS (KRAS proto-oncogene, GTPase; OMIM: 190,070) encodes one of three small guanosine triphosphatase proteins belonging to the RAS family. This group of proteins is responsible for cell proliferation, differentiation and inhibition of apoptosis. Gain-of-function variants in KRAS are commonly found in human cancers. Non-malignant somatic KRAS variants underlie a subset of RAS-associated autoimmune leukoproliferative disorders (RALD). RALD is characterized by splenomegaly, persistent monocytosis, hypergammaglobulinemia and cytopenia, but can also include autoimmune features and lymphadenopathy. In this report, we describe a non-malignant somatic variant in KRAS with prominent clinical features of massive splenomegaly, thrombocytopenia and lymphopenia. Case presentation A now-11-year-old girl presented in early childhood with easy bruising and bleeding, but had an otherwise unremarkable medical history. After consulting for the first time at 5 years of age, she was discovered to have massive splenomegaly. Clinical follow-up revealed thrombocytopenia, lymphopenia and increased polyclonal immunoglobulins and C-reactive protein. The patient had an unremarkable bone marrow biopsy, flow cytometry showed no indication of expanded double negative T-cells, while malignancy and storage disorders were also excluded. When the patient was 8 years old, whole exome sequencing performed on DNA derived from whole blood revealed a heterozygous gain-of-function variant in KRAS (NM_004985.5:c.37G > T; (p.G13C)). The variant was absent from DNA derived from a buccal swab and was thus determined to be somatic. Conclusions This case of idiopathic splenomegaly in childhood due to a somatic variant in KRAS expands our understanding of the clinical spectrum of RAS-associated autoimmune leukoproliferative disorder and emphasizes the value of securing a molecular diagnosis in children with unusual early-onset presentations with a suspected monogenic origin.

Patients with lysine-related inborn errors of metabolism (pyridoxine-dependent epilepsy [PDE] and glutaric aciduria type 1 [GA1]), follow a lysine-restricted diet with arginine-fortified lysine-free amino acid formula and additional oral arginine supplementation as a newer therapy for PDE. The rationale of arginine supplementation is based on arginine's ability to compete with lysine transport across cell membranes via shared transporter systems. Adequate doses of arginine required to competitively inhibit enteral lysine uptake has not been studied in humans This proof-of-concept study investigates the effect of incremental enteral arginine doses on whole-body lysine oxidation using an in vivo stable isotope tracer, L-[1-13 C] lysine, in healthy humans. Five healthy men completed six study days each consuming one dose of l-arginine HCl per study day; range = 50-600 mg/kg/d. Lysine intake was at DRI (30 mg/kg/d). Breath samples were analysed for L-[1-13 C] lysine oxidation to 13 CO2 using an isotope ratio mass spectrometer. Plasma amino acid concentrations were analysed using an amino acid analyser. Increasing doses of l-arginine HCl caused a linear decrease in whole-body lysine oxidation. Plasma arginine concentration increased, and plasma lysine concentration decreased below normal range with high arginine intakes. We provide the first empirical evidence of arginine-lysine antagonism in response to increasing oral arginine doses. Results suggest 300-600 mg/kg/d of l-arginine HCl and lysine intake restricted to DRI is needed to reduce enteral lysine uptake and systemic lysine oxidation. This could potentially lead to a recommended dose for arginine in lysine-related inborn errors of metabolism.

Background Morquio‐B disease (MBD) is a distinct GLB1‐related dysostosis multiplex involving the trabecular parts of long bones and spine, presenting a mild phenocopy of GALNS‐related Morquio‐A disease. Methods We analyzed 63 (n = 62 published) cases with MBD to describe their clinical, biochemical and genetic features. Results Forty‐one of 51 cases with informative clinical data had pure MBD including progressive growth impairment, kyphoscoliosis, coxa/genua valga, joint laxity, platyspondyly, odontoid hypoplasia. Ten of 51 had MBD plus neuronopathic manifestations including intellectual/developmental/speech delay, spasticity, ataxia dystonia. Corneal clouding, cardiac valve pathology, hepatosplenomegaly, spinal cord compression were infrequent and atlantooccipital dislocation, cardiomyopathy and cherry red spot were never reported. Urinary glycosaminoglycan and oligosaccharide excretion was consistently abnormal. Keratan sulphate‐derived oligosaccharides were only detected using LC‐MS/MS‐based methods. Residual β‐galactosidase activities measured against synthetic substrates were 0%‐17%. Among 28 GLB1 variants, W273 L (34/94 alleles) and T500A (11/94 alleles) occurred most frequently. W273L was invariably associated with pure MBD. Pure MBD also was reported in a case homozygous for R201H, and in the majority of cases carrying the T500A variant. Homozygous Y333C and G438E were associated with MBD plus neuronopathic manifestations. T82M, R201H, and H281Y, observed in seven alleles, previously have been found sensitive to experimental chaperones. Conclusion Data provide a basis for future systematic collection of clinical, biochemical, morphologic, and genetic data of this ultra‐rare condition.

Genomic testing is becoming routine for diagnosing rare childhood genetic disease. Evidence underlying sustainable implementation is limited, focusing on short-term endpoints such as diagnostic yield, unable to fully characterize patient and family valued outcomes. Although genomic testing is becoming widely available, evidentiary and outcomes uncertainty persist as key challenges for implementation. We examine whether the current evidence base reflects public tolerance for uncertainty for genomics to diagnose rare childhood genetic disease. We conducted focus groups with general population parents in Vancouver, Canada, and Oxford, United Kingdom, to discuss expectations and concerns related to genomic testing to diagnose rare childhood genetic disease. Applying a purposive sampling technique, recruitment continued until thematic saturation was reached. Transcripts were analysed using thematic analysis. Thirty-three parents participated across four focus groups. Participants valued causal diagnoses alongside management strategies to improve patient health and wellbeing. Further, participants valued expanding the evidence base to reduce evidentiary uncertainty while ensuring security of information. Willingness to pay out of pocket for testing reflected perceived familial health benefit. Diagnostic yield fails to fully capture valued outcomes, and efforts to resolve uncertainty better reflect public priorities. Evaluations of genomic testing that fully integrate valued endpoints are necessary to ensure consistency with best practices and public willingness to accept the uncertain familial benefit.

Notch signaling is an established developmental pathway for brain morphogenesis. Given that Delta-like 1 (DLL1) is a ligand for the Notch receptor and that a few individuals with developmental delay, intellectual disability, and brain malformations have microdeletions encompassing DLL1, we hypothesized that insufficiency of DLL1 causes a human neurodevelopmental disorder. We performed exome sequencing in individuals with neurodevelopmental disorders. The cohort was identified using known Matchmaker Exchange nodes such as GeneMatcher. This method identified 15 individuals from 12 unrelated families with heterozygous pathogenic DLL1 variants (nonsense, missense, splice site, and one whole gene deletion). The most common features in our cohort were intellectual disability, autism spectrum disorder, seizures, variable brain malformations, muscular hypotonia, and scoliosis. We did not identify an obvious genotype-phenotype correlation. Analysis of one splice site variant showed an in-frame insertion of 12 bp. In conclusion, heterozygous DLL1 pathogenic variants cause a variable neurodevelopmental phenotype and multi-systemic features. The clinical and molecular data support haploinsufficiency as a mechanism for the pathogenesis of this DLL1-related disorder and affirm the importance of DLL1 in human brain development.

Genomic testing is becoming routine for diagnosing rare childhood genetic disease. Evidence underlying sustainable implementation is limited, focusing on short-term endpoints such as diagnostic yield, unable to fully characterize patient and family valued outcomes. Although genomic testing is becoming widely available, evidentiary and outcomes uncertainty persist as key challenges for implementation. We examine whether the current evidence base reflects public tolerance for uncertainty for genomics to diagnose rare childhood genetic disease. We conducted focus groups with general population parents in Vancouver, Canada, and Oxford, United Kingdom, to discuss expectations and concerns related to genomic testing to diagnose rare childhood genetic disease. Applying a purposive sampling technique, recruitment continued until thematic saturation was reached. Transcripts were analysed using thematic analysis. Thirty-three parents participated across four focus groups. Participants valued causal diagnoses alongside management strategies to improve patient health and wellbeing. Further, participants valued expanding the evidence base to reduce evidentiary uncertainty while ensuring security of information. Willingness to pay out of pocket for testing reflected perceived familial health benefit. Diagnostic yield fails to fully capture valued outcomes, and efforts to resolve uncertainty better reflect public priorities. Evaluations of genomic testing that fully integrate valued endpoints are necessary to ensure consistency with best practices and public willingness to accept the uncertain familial benefit.

Pyridoxine-dependent epilepsy (PDE-ALDH7A1) is an autosomal recessive condition due to a deficiency of alpha-aminoadipic semialdehyde dehydrogenase, which is a key enzyme in lysine oxidation. PDE-ALDH7A1 is a developmental and epileptic encephalopathy that was historically and empirically treated with pharmacologic doses of pyridoxine. Despite adequate seizure control, most patients with PDE-ALDH7A1 were reported to have developmental delay and intellectual disability. To improve outcome, a lysine-restricted diet and competitive inhibition of lysine transport through the use of pharmacologic doses of arginine have been recommended as an adjunct therapy. These lysine-reduction therapies have resulted in improved biochemical parameters and cognitive development in many but not all patients. The goal of these consensus guidelines is to re-evaluate and update the two previously published recommendations for diagnosis, treatment, and follow-up of patients with PDE-ALDH7A1. Members of the International PDE Consortium initiated evidence and consensus-based process to review previous recommendations, new research findings, and relevant clinical aspects of PDE-ALDH7A1. The guideline development group included pediatric neurologists, biochemical geneticists, clinical geneticists, laboratory scientists, and metabolic dieticians representing 29 institutions from 16 countries. Consensus guidelines for the diagnosis and management of patients with PDE-ALDH7A1 are provided.

Global developmental delay and intellectual disability (GDD/ID) affect 3% of the paediatric population. Although inborn errors of metabolism (IEM) are not a common cause of GDD/ID, early therapeutic intervention can improve neurodevelopmental manifestations. In 2012, a first-tier test panel, including specialized metabolic and routine chemistry tests, was piloted to community-based paediatricians in British Columbia with aims to achieve earlier diagnosis of treatable IEM. Objective The aim of this retrospective review was to evaluate the diagnostic yield from these first-tier tests in the 7 years before (2006 to 2012) and after (2013 to 2019) implementation at the community paediatrician level. Results Prior and postimplementation diagnostic yield of an IEM from first-tier metabolic testing was 9 out of 986 (0.91%) and 11 out of 4,345 children (0.25%), respectively. Disorders of creatine metabolism and organic acidurias were the most frequently established diagnoses in both time periods. No diagnoses were established through acylcarnitine copper/ceruloplasmin, lactate, or ammonia testing. Twenty out of 24 patients had specific neurological or other red flag signs in addition to GDD/ID. Four boys diagnosed with an x-linked creatine transporter defect (CTD) had speech-language delay as the most prominent finding. Conclusions The expansion of first-tier metabolic testing to community-based paediatricians in BC did not yield an increase in IEM diagnoses. A modified first-tier test panel should be offered to patients with GDD/ID, neurologic, and/or red flag signs. Urine creatine testing in boys with speech-language delay warrants consideration to detect CTD.

Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare, autosomal recessive inborn error of metabolism in which several neurotransmitters including serotonin, dopamine, norepinephrine and epinephrine are deficient. Symptoms typically appear in the first year of life and include oculogyric crises and dystonia, hypotonia, and global developmental delay. Dystonia is of particular concern as a dystonic storm can ensue leading to rhabdomyolysis. Rhabdomyolysis can become life-threating and therefore its recognition and prompt management is of significant importance. Here we present two cases of patients with AADC deficiency and a history of dystonic crisis causing rhabdomyolysis. We hypothesize that in addition to the hypodopaminergic, a hypercholinergic state is contributing to the pathophysiology of dystonia in AADC deficiency, as well as to the associated rhabdomyolysis. We were able to prevent rhabdomyolysis in both patients with using Dantrolene and we suggest using a trial of this medication in cases of sustained dystonic crisis in AADC deficiency patients.

Morquio B disease (MBD) is an autosomal recessive GLB1-gene-related lysosomal storage disease, presenting with a peculiar type of dysostosis multiplex which is also observed in GALNS-related Morquio A disease. MBD may present as pure skeletal phenotype (pure MBD) or in combination with the neuronopathic manifestations seen in type 2 (juvenile) or type 3 (late onset) GM1 gangliosidosis (MBD plus). The main skeletal features are progressive growth impairment, kyphoscoliosis, coxa/genua valga, joint laxity, platyspondyly and odontoid hypoplasia. The main neuronopathic features are dystonia, ataxia, and intellectual/developmental/speech delay. Spinal cord compression occurs as a complication of spinal dysostosis. Chronic pain is reported, along with mobility issues and challenges with daily living and self-care activities, as the most common health concern. The most commonly reported orthopedic surgeries are hip and knee replacements. Keratan sulphate-derived oligosaccharides are characteristic biomarkers. Residual β-galactosidase activities measured against synthetic substrates do not correlate with the phenotype. W273 L and T500A are the most frequently observed GLB1 variants in MBD, W273L being invariably associated with pure MBD. Cytokines play a role in joint destruction and pain, providing a promising treatment target. In the future, patients may benefit from small molecule therapies, and gene and enzyme replacement therapies, which are currently being developed for GM1 gangliosidosis.

Morquio B disease (MBD) or Mucopolysaccharidosis type IV B (MPS IV B) is caused by particular GLB1 mutations specifically affecting the affinity of beta-galactosidase to keratan sulphate, resulting in dysostosis multiplex resembling Morquio A (MPS IV A) disease (GALNS deficiency). Additional neuronopathic features of GM1 II/III (juvenile/adult) gangliosidosis have been reported in some patients. Our patient/caregiver online survey was aimed at elucidating the clinical manifestations of this ultra-rare condition.Comparing to previously published data on MPS IV A, the 30 respondents in our MBD group presented with greater growth chart values (weight and height) and with lesser effects of odontoid hypoplasia. The most common concerns are: (1) mobility issues - 84% having difficulty walking; (2) chronic pain - 96%; (3) surgeries - average 3 per person, 80% for hip problems; (4) hip dysplasia, knee/ankle concerns, and scoliosis. Approximately 50% of MBD participants live independently and actively contributing to society.Evidence from our survey results supports the notion that skeletal manifestations in MBD are milder than in the majority of patients with MPS IV A. The data collected will help with the establishment of clinically meaningful outcomes for future therapeutic trials, and with the counseling of newly diagnosed patients about their health expectations. Keywords: Skeletal dysplasia, GM1 gangliosidosis, Lysosome, Natural history

Background The Canadian Inherited Metabolic Diseases Research Network (CIMDRN) is a pan-Canadian practice-based research network of 14 Hereditary Metabolic Disease Treatment Centres and over 50 investigators. CIMDRN aims to develop evidence to improve health outcomes for children with inherited metabolic diseases (IMD). We describe the development of our clinical data collection platform, discuss our data quality management plan, and present the findings to date from our data quality assessment, highlighting key lessons that can serve as a resource for future clinical research initiatives relating to rare diseases. Methods At participating centres, children born from 2006 to 2015 who were diagnosed with one of 31 targeted IMD were eligible to participate in CIMDRN’s clinical research stream. For all participants, we collected a minimum data set that includes information about demographics and diagnosis. For children with five prioritized IMD, we collected longitudinal data including interventions, clinical outcomes, and indicators of disease management. The data quality management plan included: design of user-friendly and intuitive clinical data collection forms; validation measures at point of data entry, designed to minimize data entry errors; regular communications with each CIMDRN site; and routine review of aggregate data. Results As of June 2019, CIMDRN has enrolled 798 participants of whom 764 (96%) have complete minimum data set information. Results from our data quality assessment revealed that potential data quality issues were related to interpretation of definitions of some variables, participants who transferred care across institutions, and the organization of information within the patient charts (e.g., neuropsychological test results). Little information was missing regarding disease ascertainment and diagnosis (e.g., ascertainment method – 0% missing). Discussion Using several data quality management strategies, we have established a comprehensive clinical database that provides information about care and outcomes for Canadian children affected by IMD. We describe quality issues and lessons for consideration in future clinical research initiatives for rare diseases, including accurately accommodating different clinic workflows and balancing comprehensiveness of data collection with available resources. Integrating data collection within clinical care, leveraging electronic medical records, and implementing core outcome sets will be essential for achieving sustainability.

Pyruvate carboxylase (PC) is a biotin-containing enzyme that is responsible for the adenosine triphosphate-dependent carboxylation of pyruvate to oxaloacetate, a key intermediate in the tricarboxylic acid cycle. PC deficiency (OMIM 266150) is a rare autosomal recessive metabolic disease, causing elevation of pyruvate, lactate, and alanine. Three types of PC deficiency have been described in the literature; A, B, and C. Type A PC deficiency, also called infantile or North American type, is characterized by infantile onset acidosis, failure to thrive, and developmental delay. The second subtype or type B, the neonatal or French form, presents usually in the neonatal period, mostly in the first 72 hours of life with severe lactic acidosis, truncal hypotonia, and seizures. The third type is called type C, is extremely rare with few cases published in the literature. In this case report, we present an 11-month-old girl who presented with acute flaccid paralysis, lethargy, and constipation with elevated ketones and lactate. She was confirmed genetically and biochemically to have PC deficiency type C. The patient's unusual presentation expands the clinical phenotype of this extremely rare disease.

Background Phenylketonuria is characterized by mutations in the Phe hydroxylase gene that leads to the accumulation of Phe in plasma and the brain. The standard of care for phenylketonuria is nutritional management with dietary restriction of Phe and the provision of sufficient protein and energy for growth and health maintenance. The protein requirement in children with phenylketonuria is empirically determined based upon phenylketonuria nutritional guidelines that are adjusted individually in response to biochemical markers and growth. Objective We determined dietary protein requirements in children with phenylketonuria with the use of the indicator amino acid oxidation (IAAO) technique, with l-[1-13C]Leu as the indicator amino acid. Methods Four children (2 males; 2 females) aged 9-18 y with phenylketonuria [mild hyperphenylalanemia (mHPA); 6-10 mg/dL (360-600 μmol/L)] were recruited to participate in ≥7 separate test protein intakes (range: 0.2-3.2 g ⋅ kg-1 ⋅ d-1) with the IAAO protocol with the use of l-[1-13C]Leu followed by the collection of breath and urine samples over 8 h. The diets were isocaloric and provided energy at 1.7 times the resting energy expenditure. Protein was provided as a crystalline amino acid mixture based on an egg protein pattern, except Phe and Leu, which were maintained at a constant across intakes. Protein requirement was determined with the use of a 2-phase linear-regression crossover analysis of the rate of l-[1-13C]Leu tracer oxidation. Results The mean protein requirement was determined to be 1.85 g ⋅ kg-1 ⋅ d-1 (R2 = 0.66; 95% CI: 1.37, 2.33). This result is substantially higher than the 2014 phenylketonuria recommendations (1.14-1.33 g ⋅ kg-1 ⋅ d-1; based on 120-140% above the current RDA for age). Conclusions To our knowledge, this is the first study to directly define a quantitative requirement for protein intake in children with mHPA and indicates that current protein recommendations in children with phenylketonuria may be insufficient. This trial was registered at clinicaltrials.gov as NCT01965691.

Background Profiling the entire genome at base pair resolution in a single test offers novel insights into disease by means of dissection of genetic contributors to phenotypic features. Methods We performed genome sequencing for a patient who presented with atypical hereditary sensory and autonomic neuropathy, severe epileptic encephalopathy, global developmental delay, and growth hormone deficiency. Results Assessment of the variants detected by mapped sequencing reads followed by Sanger confirmation revealed that the proband is a compound heterozygote for rare variants within RETREG1 (FAM134B), a gene associated with a recessive form of hereditary sensory and autonomic neuropathy, but not with epileptic encephalopathy or global developmental delay. Further analysis of the data also revealed a heterozygous missense variant in DNM1L, a gene previously implicated in an autosomal dominant encephalopathy, epilepsy, and global developmental delay and confirmed by Sanger sequencing to be a de novo variant not present in parental genomes. Conclusions Our findings emphasize the importance of genome‐wide sequencing in patients with a well‐characterized genetic disease with atypical presentation. This approach reduces the potential for misdiagnoses.

Background: Guanidinoacetate methyltransferase (GAMT) deficiency is a rare disorder of creatine biosynthesis presenting with epilepsy and developmental delay in infancy. Excellent developmental outcomes have been reported for infants treated from birth due to a family history. The BC Newborn Screening Program initiated a 3 year pilot screening study for GAMT deficiency to evaluate the performance of a novel three-tiered screening approach. Methods: Over 36 months all bloodspots submitted for routine newborn screening were included in the pilot study (de-identified). Initial GAA measurement was integrated into the standard acylcarnitine/amino acid first-tier assay. All samples with elevated GAA were subjected to second-tier GAA analysis by LC-MS/MS integrated into an existing branched-chain amino acid (MSUD) method. GAMT gene sequencing was completed on the original bloodspot for all specimens with elevated GAA on the second-tier test. The protocol allowed for re-identification for treatment of any specimen with one or two likely pathogenic GAMT mutations. Results: Over the study period 135,372 specimens were tested with 259 (0.19%) over the first-tier GAA cut-off. The second-tier assay removed an interference falsely elevating GAA levels, and only 3 samples required genotyping. No mutations were identified in any samples, all were deemed negative screens and no follow-up was initiated. Conclusions: A three-tier algorithm for GAMT newborn screening showed excellent test performance with zero false positives. No cases were detected, supporting a low incidence for this disorder. Given the low incremental costs and evidence of positive outcomes with early intervention, GAMT deficiency remains an excellent candidate for newborn screening. (C) 2016 Elsevier Inc. All rights reserved

Background Pyridoxine-dependent epilepsy is a rare autosomal recessive epileptic encephalopathy caused by antiquitin ( ALDH7A1 ) deficiency. In spite of adequate seizure control, 75% of patients suffer intellectual developmental disability. Antiquitin deficiency affects lysine catabolism resulting in accumulation of α-aminoadipic semialdehyde/pyrroline 6′ carboxylate and pipecolic acid. Beside neonatal refractory epileptic encephalopathy, numerous neurological manifestations and metabolic/biochemical findings have been reported. Methods and Results We present a phenotypic spectrum of antiquitin deficiency based on a literature review (2006 to 2015) of reports (n = 49) describing the clinical presentation of confirmed patients (n > 200) and a further six patient vignettes. Possible presentations include perinatal asphyxia; neonatal withdrawal syndrome; sepsis; enterocolitis; hypoglycemia; neuroimaging abnormalities (corpus callosum and cerebellar abnormalities, hemorrhage, white matter lesions); biochemical abnormalities (lactic acidosis, electrolyte disturbances, neurotransmitter abnormalities); and seizure response to pyridoxine, pyridoxal-phosphate, and folinic acid dietary interventions. Discussion The phenotypic spectrum of pyridoxine-dependent epilepsy is wide, including a myriad of neurological and systemic symptoms. Its hallmark feature is refractory seizures during the first year of life. Given its amenability to treatment with lysine-lowering strategies in addition to pyridoxine supplementation for optimal seizure control and developmental outcomes, early diagnosis of pyridoxine-dependent epilepsy is essential. All infants presenting with unexplained seizures should be screened for antiquitin deficiency by determination of α-aminoadipic semialdehyde/pyrroline 6′ carboxylate (in urine, plasma or cerebrospinal fluid) and ALDH7A1 molecular analysis.

We describe neurotransmitter abnormalities in two patients with drug-resistant epilepsy resulting from deleterious de novo mutations in sodium channel genes. Whole exome sequencing identified a de novo SCN2A splice-site mutation (c.2379 +1G>A, p.G1u717Gly.fs*30) resulting in deletion of exon 14, in a 10-year old male with early onset global developmental delay, intermittent ataxia, autism, hypotonia, epileptic encephalopathy and cerebral/cerebellar atrophy. In the cerebrospinal fluid both homovanillic acid and 5-hydroxyindoleacetic acid were significantly decreased; extensive biochemical and genetic investigations ruled out primary neurotransmitter deficiencies and other known inborn errors of metabolism. In an 8-year old female with an early onset intractable epileptic encephalopathy, developmental regression, and progressive cerebellar atrophy, a previously unreported de novo missense mutation was identified in SCN8A (c.5615G>A; p.Arg1872GIn), affecting a highly conserved residue located in the C-terminal of the Na(v)1.6 protein. Aside from decreased homovanillic acid and 5-hydroxyindoleacetic acid, 5-methyltetrahydrofolate was also found to be low. We hypothesize that these channelopathies cause abnormal synaptic mono-amine metabolite secretion/uptake via impaired vesicular release and imbalance in electrochemical ion gradients, which in turn aggravate the seizures. Treatment with oral 5-hydroxytryptophan, L-Dopa/Carbidopa, and a dopa agonist resulted in mild improvement of seizure control in the male case, most likely via dopamine and serotonin receptor activated signal transduction and modulation of glutamatergic, GABA-ergic and glycinergic neurotransmission. Neurotransmitter analysis in other sodium channelopathy patients will help validate our findings, potentially yielding novel treatment opportunities. (C) 2015 Elsevier Inc. All rights reserved

Background Arginine:glycine aminotransferase (AGAT) (GATM) deficiency is an autosomal recessive inborn error of creative synthesis. Objective We performed an international survey among physicians known to treat patients with AGAT deficiency, to assess clinical characteristics and long-term outcomes of this ultra-rare condition. Results 16 patients from 8 families of 8 different ethnic backgrounds were included. 1 patient was asymptomatic when diagnosed at age 3 weeks. 15 patients diagnosed between 16 months and 25 years of life had intellectual disability/developmental delay (IDD). 8 patients also had myopathy/proximal muscle weakness. Common biochemical denominators were low/undetectable guanidinoacetate (GAA) concentrations in urine and plasma, and low/undetectable cerebral creatine levels. 3 families had protein truncation/null mutations. The rest had missense and splice mutations. Treatment with creatine monohydrate (100–800 mg/kg/day) resulted in almost complete restoration of brain creatine levels and significant improvement of myopathy. The 2 patients treated since age 4 and 16 months had normal cognitive and behavioral development at age 10 and 11 years. Late treated patients had limited improvement of cognitive functions. Conclusion AGAT deficiency is a treatable intellectual disability. Early diagnosis may prevent IDD and myopathy. Patients with unexplained IDD with and without myopathy should be assessed for AGAT deficiency by determination of urine/plasma GAA and cerebral creatine levels (via brain MRS), and by GATM gene sequencing.

Inborn errors of metabolism (IEM) represent the first group of genetic disorders, amenable to causal therapies. In addition to traditional medical diet and cofactor treatments, new treatment strategies such as enzyme replacement and small molecule therapies, solid organ transplantation, and cell‐and gene‐based therapies have become available. Inherent to the rare nature of the single conditions, generating high‐quality evidence for these treatments in clinical trials and under real‐world conditions has been challenging. Guidelines developed with standardized methodologies have contributed to improve the practice of care and long‐term clinical outcomes. Adaptive trial designs allow for changes in sample size, group allocation and trial duration as the trial proceeds. n‐of‐1 studies may be used in small sample sized when participants are clinically heterogeneous. Multicenter observational and registry‐based clinical trials are promoted via international research networks. Core outcome and standard data element sets will enhance comparative analysis of clinical trials and observational studies. Patient‐centered outcome‐research as well as patient‐led research initiatives will further accelerate the development of therapies for IEM.

Introduction For many rare diseases, strong analytic study designs for evaluating the efficacy and effectiveness of interventions are challenging to implement because of small, geographically dispersed patient populations and underlying clinical heterogeneity. The objective of this study was to integrate perspectives from published literature and key rare disease stakeholders to better understand the perceived challenges and proposed methodological approaches to research on clinical interventions for rare diseases. Methods We used a meta-narrative literature review and focus group interviews with key rare disease stakeholders to better understand the perceived challenges in generating and synthesizing treatment effectiveness evidence, and to describe various research methods for mitigating these identified challenges. Data from both components of this study were synthesized narratively according to research paradigms that emerged from our data. Results Results from our meta-narrative literature review and focus group interviews revealed three fundamental challenges in generating robust treatment effectiveness evidence for rare diseases: i) limitations in recruiting a sufficient sample size to achieve planned statistical power; ii) inability to account for clinical heterogeneity and assess treatment effects across a clinical spectrum; and iii) reliance on short-term, surrogate outcomes whose clinical relevance is often unclear. We mapped these challenges and associated solutions to three interrelated research paradigms: i) explanatory evidence generation; ii) comparative effectiveness/pragmatic evidence generation; and iii) patient-oriented evidence generation. Within each research paradigm, numerous criticisms and potential solutions have been described with respect to overcoming these challenges from a research study design perspective. Conclusions Over time, discussions about clinical research for interventions for rare diseases have moved beyond methodological approaches to overcome challenges related to explanatory evidence generation, with increased recognition of the importance of pragmatic and patient-oriented evidence. Future directions for our work include developing a framework to expand current evidence synthesis practices to take into consideration many of the concepts discussed in this paper. Electronic supplementary material The online version of this article (10.1186/s13023-018-0851-1) contains supplementary material, which is available to authorized users.

Glycogen storage disease (GSD) type 1 is a rare autosomal recessive inherited condition. The 1b subtype comprises the minority of cases, with an estimated prevalence of 1 in 500,000 children. Patients with glycogen storage disease type 1b are often treated with granulocyte colony stimulating factor (G-CSF) for prolonged periods to improve symptoms of inflammatory bowel disease (IBD) and in the face of severe neutropenia to decrease risk of infection. Long-term G-CSF treatment may result in an increased risk of myelodysplastic syndrome (MDS) or acute myeloid leukemia (AML) possibly due to increased marrow stress resulting in telomere shortening. To our knowledge, there have been two published cases of AML in GSD type 1b patients following long-term G-CSF exposure. Here, we report two further cases of AML/MDS-related changes in patients GSD type 1b treated with G-CSF. One patient developed AML with complex karyotype after 20 years of G-CSF treatment. The second patient was found to have short telomeres after 10 years of G-CSF exposure, but no evidence of acute leukemia at present. The third patient developed AML/MDS after 25 years of G-CSF use, with short telomeres prior to bone marrow transplant. Together these cases suggest that GSD type 1b patients with prolonged G-CSF exposure may be at an increased risk of MDS/AML states associated with G-CSF-induced shortened telomeres. We recommend that any GSD1b patients with prolonged G-CSF should have routine telomere assessments with monitoring for MDS if telomere shortening is observed, and with particular attention warranted if there is unexplained loss of G-CSF responsiveness.

Background:Secondary neurotransmitter deficiencies have been reported in several reviews. Our primary aim was to assess the relationship among epilepsy, antiseizure medications, and specific neurotransmitter abnormalities. We also evaluated movement disorders and brain abnormalities via magnetic resonance imaging scans in patients with secondary neurotransmitter defects.Methods:This is a retrospective case series of 376 patients who underwent neurotransmitter analysis at BC Children’s Hospital between 2009 and 2013, for a variety of neurological presentations. The biochemical genetics laboratory database was interrogated for results of cerebrospinal fluid neurotransmitter analyses. Clinical data for patients with abnormal results were collected from the hospital charts. Statistical analysis included one-way analysis of variance, chi-square, and a two-way contingency table.Results:Abnormal neurotransmitter values were identified in 67 (17.8%) patients, two (0.53%) of which were attributable to a congenital neurotransmitter disorder and 11 (16.9%) secondary to other genetic diagnoses. Of 64 patients with secondary abnormal neurotransmitter values, 38 (59%) presented with epilepsy and 20 (31%) with movement disorders. A combination of epilepsy and movement disorder was less frequent.Discussion:Acknowledging the limitations of this retrospective chart review, we conclude that, in our cohort, in addition to patients with movement disorders, a considerable number of patients with epilepsy and epileptic encephalopathy also showed secondary neurotransmitter mono-amine abnormalities. There is no clear relation, however, between clinical phenotype and type of neurotransmitter affected. In addition, no association was identified between the type of antiseizure medications and affected neurotransmitter type. We outline the need for prospective studies to further enrich our understanding of the relation between epilepsy and neurotransmitters with a focus on improving treatments and patient outcomes.

The role of disturbed chromatin remodeling in the pathogenesis of intellectual disability (ID) is well established and illustrated by de novo mutations found in a plethora of genes encoding for proteins of the epigenetic regulatory machinery. We describe mutations in the “SET nuclear proto-oncogene” (SET), encoding a component of the “inhibitor of histone acetyltransferases” (INHAT) complex, involved in transcriptional silencing. Using whole exome sequencing, four patients were identified with de novo mutations in the SET gene. Additionally, an affected mother and child were detected who carried a frameshift variant in SET. Four patients were found in literature. The de novo mutations in patients affected all four known SET mRNA transcripts. LoF mutations in SET are exceedingly rare in the normal population and, if present, affect only one transcript. The pivotal role of SET in neurogenesis is evident from in vitro and animal models. SET interacts with numerous proteins involved in histone modification, including proteins encoded by known autosomal dominant ID genes, that is, EP300, CREBBP, SETBP1, KMT2A, RAC1, and CTCF. Our study identifies SET as a new component of epigenetic regulatory modules underlying human cognitive disorders, and as a first member of the Nucleosome Assembly Protein (NAP) family implicated in ID.

Background Phenylketonuria (PKU) is an autosomal recessive disorder caused by deficiency of hepatic phenylalanine hydroxylase (PAH) leading to increased levels of phenylalanine in the plasma. Phenylalanine levels and phenylalanine hydroxylase (PAH) activity monitoring are currently limited to conventional blood dot testing. 1- 13 C-phenylalanine, a stable isotope can be used to examine phenylalanine metabolism, as the conversion of phenylalanine to tyrosine occurs in vivo via PAH and subsequently releases the carboxyl labeled 13 C as 13 CO 2 in breath. Objective Our objective was to examine phenylalanine metabolism in children with PKU using a minimally-invasive 1- 13 C-phenylalanine breath test ( 13 C-PBT). Design Nine children (7M: 2F, mean age 12.5±2.87y) with PKU participated in the study twice: once before and once after sapropterin supplementation. Children were provided 6mg/kg oral dose of 1- 13 C-phenylalanine and breath samples were collected at 20min intervals for a period of 2h. Rate of CO 2 production was measured at 60min post-oral dose using indirect calorimetry. The percentage of 1- 13 C-phenylalanine exhaled as 13 CO 2 was measured over a 2h period. Prior to studying children with PKU, we tested the study protocol in healthy children (n=6; 4M: 2F, mean age 10.2±2.48y) as proof of principle. Results Production of a peak enrichment (C max ) of 13 CO 2 (% of dose) in all healthy children occurred at 20min ranging from 17–29% of dose, with a subsequent return to ~5% by the end of 2h. Production of 13 CO 2 from 1- 13 C-phenylalanine in all children with PKU prior to sapropterin treatment remained low. Following sapropterin supplementation for a week, production of 13 CO 2 significantly increased in five children with a subsequent decline in blood phenylalanine levels, suggesting improved PAH activity. Sapropterin treatment was not effective in three children whose 13 CO 2 production remained unchanged, and did not show a reduction in blood phenylalanine levels and improvement in dietary phenylalanine tolerance. Conclusions Our study shows that the 13 C-PBT can be a minimally invasive, safe and reliable measure to examine phenylalanine metabolism in children with phenylketonuria. The breath data are corroborated by blood phenylalanine levels in children who had increased responses in 13 CO 2 production, as reviewed post-hoc from clinical charts.

We analyzed long-term sustainability of improved blood Phenylalanine (Phe) control and changes to dietary Phe tolerance in 11 patients (1 month to 16 years), with various forms of primary PAH deficiency (classic, moderate, severe phenylketonuria [PKU], mild hyperphenylalaninemia [HPA]), who were treated with 15-20mg/kg/d Sapropterin-dihydrochloride during a period of 13-44 months. 7/11 patients had a sustainable, significant reduction of baseline blood Phe concentrations and 6 of them also had an increase in mg/kg/day Phe tolerance. In 2 patients with mild HPA, blood Phe concentrations remained in the physiologic range even after a 22 and 36% increase in mg/kg/day Phe tolerance and an achieved Phe intake at 105% and 268% of the dietary reference intake (DRI) for protein. 2 of these responders had classic PKU. 1 patient with mild HPA who started treatment at 2 months of life, had a significant and sustainable reduction in pretreatment blood Phe concentrations, but no increase in the mg/kg/day Phe tolerance. An increase in Phe tolerance could only be demonstrated when expressing the patient's daily Phe tolerance with the DRI for protein showing an increase from 58% at baseline to 78% of normal DRI at the end of the observation. Long-term follow-up of patients with an initial response to treatment with Sapropterin is essential to determine clinically meaningful outcomes. Phenylalanine tolerance should be expressed in mg/kg/day and/or % of normal DRI to differentiate medical therapy related from physiologic growth related increase in daily Phe intake.

Background: Creatine transporter deficiency (CTD) is an X-linked inborn error of creatine metabolism characterized by reduced intra-cerebral creatine, developmental delay/intellectual disability, (ID), behavioral disturbance, seizures, and hypotonia in individuals harboring mutations in the SLC6A8 gene. Treatment for CTD includes supplementation with creatine, either alone or in combination with creatine precursors (arginine or glycine). Unlike other disorders of creatine metabolism, the efficacy of its treatment remains controversial. Methods: We present our systematic literature review (2001-2013) comprising 7 publications (case series/reports), collectively describing 25 patients who met the inclusion criteria, and 3 additional cases treated at our institution. Definitions were established and extracted data analyzed for cognitive ability, psychiatric and behavioral disturbances, epilepsy, and cerebral proton magnetic resonance spectroscopy measurements at pre- and post-treatment. Results: Treatment regimens varied among the 28 cases: 2 patients received creatine-monohydrate supplementation; 7 patients received L-arginine; 2 patients received creatine-monohydrate and L-arginine; and 17 patients received a combination of creatine-monohydrate, L-arginine and glycine. Median treatment duration was 34.6 months (range 3 months-5 years). Level of evidence was IV. A total of 10 patients (36%) demonstrated response to treatment, manifested by either an increase in cerebral creatine, or improved clinical parameters. Seven of the 28 patients had quantified pre- and post-treatment creatine, and it was significantly increased post-treatment. All of the patients with increased cerebral creatine also experienced clinical improvement In addition, the majority of patients with clinical improvement had detectable cerebral creatine prior to treatment. 90% of the patients who improved were initiated on treatment before nine years of age. Conclusions: Acknowledging the limitations of this systematic review, we conclude that a proportion of CTD patients show amenability to treatment-particularly milder cases with residual brain creatine, and therefore probable residual protein function. We propose systematic screening for CTD in patients with ID, to allow early initiation of treatment, which currently comprises oral creatine, arginine and/or glycine supplementation. Standardized monitoring for safety and evaluation of treatment effects are required in all patients. This study provides effectiveness on currently available treatment, which can be used to discern effectiveness of future interventions (e.g. cyclocreatine). (C) 2014 Elsevier Inc. All rights reserved

Background:Identification of the underlying cause of intellectual disability (ID) is important as it improves genetic counselling, management, adaptation; yet its etiologic heterogeneity is challenging and often leads to an expensive work-up.Methods:To improve this diagnostic trajectory, the multidisciplinary Complex Diagnostic Clinic (CDC) was established for ID patients with unexplained complex systemic and/or neurologic features that were referred to the CDC and evaluated by three medical specialists followed by multi-disciplinary rounds. Analyses included surveys and interviews, (retrospective) chart review, costs calculations and comparison.Results:24 children (9 male) were evaluated during seven clinics held over 16 months. The average patient age was 7 years 11 months (range 9 months-18 years). All the children had previously been seen by 2–10 specialist services. The diagnostic yield of the CDC was higher than expected with confirmed and working diagnoses in 11 (46%) and 9 (38%) children respectively. Cost-savings included fewer trips to hospital and fewer tests via more streamlined evaluations. Positive feedback was received from both families and medical professionals.Conclusions:The CDC represents an innovative model of personalized care. Specialist collaboration in the interpretation of relevant clinical, biochemical and genomic data resulted in diagnoses, where none had previously been possible.

We are reporting a retrospective review of blood phenylalanine (Phe) concentrations in 33 patients with classical phenylketonuria (PKU) born between 1991 and 2009 and continuously followed up in our clinic in 2009. As an indicator of blood Phe control, we analysed the percentage of blood Phe concentrations within and outside of the treatment range for each individual for treatment periods between 1 month and 12 months, 1 to 6 years, and 6 to 12 years of age. Despite early diagnosis and medical management in a centralized care model, only approximately 40% of patients had 60% and more of their blood Phe concentrations within the treatment range during their lifetime treatment periods. There was no statistical difference for the percentage of blood Phe concentrations within the treatment range, the mean Phe concentrations or the SD between the various treatment periods. We found a correlation between Phe tolerance and percentage of blood Phe concentrations within the treatment range. Patients born between 1991 and 1999 had poorer control than those born later. A frequent quality assurance audit is recommended to assess treatment outcomes in clinics providing care to children with PKU.

BACKGROUND: Whole-exome sequencing has transformed gene discovery and diagnosis in rare diseases. Translation into disease-modifying treatments is challenging, particularly for intellectual developmental disorder. However, the exception is inborn errors of metabolism, since many of these disorders are responsive to therapy that targets pathophysiological features at the molecular or cellular level.METHODS: To uncover the genetic basis of potentially treatable inborn errors of metabolism, we combined deep clinical phenotyping (the comprehensive characterization of the discrete components of a patient's clinical and biochemical phenotype) with whole-exome sequencing analysis through a semiautomated bioinformatics pipeline in consecutively enrolled patients with intellectual developmental disorder and unexplained metabolic phenotypes.RESULTS: We performed whole-exome sequencing on samples obtained from 47 probands. Of these patients, 6 were excluded, including 1 who withdrew from the study. The remaining 41 probands had been born to predominantly nonconsanguineous parents of European descent. In 37 probands, we identified variants in 2 genes newly implicated in disease, 9 candidate genes, 22 known genes with newly identified phenotypes, and 9 genes with expected phenotypes; in most of the genes, the variants were classified as either pathogenic or probably pathogenic. Complex phenotypes of patients in five families were explained by coexisting monogenic conditions. We obtained a diagnosis in 28 of 41 probands (68%) who were evaluated. A test of a targeted intervention was performed in 18 patients (44%).CONCLUSIONS: Deep phenotyping and whole-exome sequencing in 41 probands with intellectual developmental disorder and unexplained metabolic abnormalities led to a diagnosis in 68%, the identification of 11 candidate genes newly implicated in neurometabolic disease, and a change in treatment beyond genetic counseling in 44%. (Funded by BC Children's Hospital Foundation and others.).

The metabolic control of phenylalanine levels is a challenge during illness. We present the metabolic management of a 6 year old boy with classical PKU who was diagnosed with stage III intraabdominal Burkit's lymphoma and underwent surgical resection and chemotherapy. The metabolic control during chemotherapy was achieved by the use of parenteral custom made amino acid solution and pro-active adjustment of intake. From the 94 obtained plasma phenylalanine (Phe) levels, 18.4% were above our clinic's recommended upper limit (360 μmol/L, 6 mg/dL) while 52.7% of Phe levels were below the recommended lower limit (120 μmol/L, 2 mg/dL). Phe levels above recommended range were associated with low caloric/protein intake, while levels below recommended range reflected the difficulty in achieving the full prescribed Phe intake. We recommend early institution of custom made amino acid solution with maximum amino acid content and caloric intake to provide optimal phenylalanine control. Administration of phenylalanine via regular intravenous amino acid solution may assist in avoiding low Phe levels when prescribed intake is compromised due to vomiting and other disease related illnesses. Use of custom made, phenylalanine free amino acid solution proved beneficial in the management of blood phenylalanine levels in a PKU patient during chemotherapy for Burkitt lymphoma.

Pyridoxine-dependent epilepsy (PDE) was first described in 1954. The ALDH7A1 gene mutations resulting in α-aminoadipic semialdehyde dehydrogenase deficiency as a cause of PDE was identified only in 2005. Neonatal epileptic encephalopathy is the presenting feature in >50% of patients with classic PDE. We report the case of a 13-month-old girl with profound neonatal hypoglycemia (0.6 mmol/L; reference range >2.4), lactic acidosis (11 mmol/L; reference range A (p.Val278Val), and a novel putative pathogenic missense mutation c.1192G>C (p.Gly398Arg) in the ALDH7A1 gene. She has been seizure-free since 1.5 months of age on treatment with pyridoxine alone. She has motor delay and central hypotonia but normal language and social development at the age of 13 months. This case is the first description of a patient with PDE due to mutations in the ALDH7A1 gene who presented with profound neonatal hypoglycemia and lactic acidosis masquerading as a neonatal-onset gluconeogenesis defect. PDE should be included in the differential diagnosis of hypoglycemia and lactic acidosis in addition to medically refractory neonatal seizures.

Cobalamin F disease (cblF) is a rare disorder of intracellular cobalamin metabolism resulting in failure to thrive, recurrent stomatitis, skin rash, megaloblastic anemia, hypotonia, seizures, and intellectual disability. Data on long-term outcomes are not available. We report on the outcome of a patient with cblF disease with a frameshift mutation in the LMBRD1 gene after 18 years of intramuscular hydroxycobalamin treatment.