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Background: In 2014, germline signal transducer and activator of transcription (STAT) 3 gain-of-function (GOF) mutations were first described to cause a novel multisystem disease of early-onset lymphoproliferation and autoimmunity. Objective: This pivotal cohort study defines the scope, natural history, treatment, and overall survival of a large global cohort of patients with pathogenic STAT3 GOF variants. Methods: We identified 191 patients from 33 countries with 72 unique mutations. Inclusion criteria included symptoms of immune dysregulation and a biochemically confirmed germline heterozygous GOF variant in STAT3. Results: Overall survival was 88%, median age at onset of symptoms was 2.3 years, and median age at diagnosis was 12 years. Immune dysregulatory features were present in all patients: lymphoproliferation was the most common manifestation (73%); increased frequencies of double-negative (CD4−CD8−) T cells were found in 83% of patients tested. Autoimmune cytopenias were the second most common clinical manifestation (67%), followed by growth delay, enteropathy, skin disease, pulmonary disease, endocrinopathy, arthritis, autoimmune hepatitis, neurologic disease, vasculopathy, renal disease, and malignancy. Infections were reported in 72% of the cohort. A cellular and humoral immunodeficiency was observed in 37% and 51% of patients, respectively. Clinical symptoms dramatically improved in patients treated with JAK inhibitors, while a variety of other immunomodulatory treatment modalities were less efficacious. Thus far, 23 patients have undergone bone marrow transplantation, with a 62% survival rate. Conclusion:: STAT3 GOF patients present with a wide array of immune-mediated disease including lymphoproliferation, autoimmune cytopenias, and multisystem autoimmunity. Patient care tends to be siloed, without a clear treatment strategy. Thus, early identification and prompt treatment implementation are lifesaving for STAT3 GOF syndrome.

Determining the cause of a low neutrophil count in a pediatric or adult patient is essential for the hematologist's clinical decision-making. Fundamental to this diagnostic process is establishing the presence or lack of a mature neutrophil storage pool, as absence places the patient at higher risk for infection and the need for supportive care measures. Many diagnostic tests, eg, a peripheral blood smear and bone marrow biopsy, remain important tools, but greater understanding of the diversity of neutropenic disorders has added new emphasis on evaluating for immune disorders and genetic testing. In this article, a structure is provided to assess patients based on the mechanism of neutropenia and to prioritize testing based on patient age and hypothesized pathophysiology. Common medical quandaries including fever management, need for growth factor support, risk of malignant transformation, and curative options in congenital neutropenia are reviewed to guide medical decision-making in neutropenic patients.

Quality of life (QOL) and patient-reported outcomes (PROs) assessments in immunodeficiency patients, including those with chronic severe neutropenia conditions, are imperative to determining modifiable health-related features to optimize care. We present the largest study to date of QOL in those with chronic severe neutropenia conditions with further evaluation of patient provider satisfaction and patient-reported outcome measures. Subjects completed electronic surveys assessing QOL, PROs, and patient provider satisfaction. There is a significantly negative impact of a chronic severe neutropenia disorder on QOL, fatigue, physical function, cognitive function and pain in adult patients when compared to controls. Children with a chronic neutropenia condition had comparable QOL to controls, but reported fewer depressive symptoms, improved mobility, and stronger self-reported peer relationships. Adults had worse scores for QOL, depression and fatigue when compared to children. Adult and pediatric chronic severe neutropenia patients or their caregivers felt that their medical provider was compassionate, trustworthy, and accessible. However, less than 50% of adult patients agreed their clinician had excellent expertise in white blood cell disorders. Chronic neutropenia complexly affect QOL and PROs. An analysis of these parameters allows for targeted interventions to improve patient psychosocial, physical and neurocognitive health.

Haploinsufficiency of suppressor of cytokine signaling 1 (SOCS1) is a recently discovered autoinflammatory disorder with significant rheumatologic, immunologic, and hematologic manifestations. Here we report a case of SOCS1 haploinsufficiency in a 5-year-old child with profound arthralgias and immune-mediated thrombocytopenia unmasked by SARS-CoV-2 infection. Her clinical manifestations were accompanied by excessive B cell activity, eosinophilia, and elevated IgE levels. Uniquely, this is the first report of SOCS1 haploinsufficiency in the setting of a chromosomal deletion resulting in complete loss of a single SOCS1 gene with additional clinical findings of bone marrow hypocellularity and radiologic evidence of severe enthesitis. Immunologic profiling showed a prominent interferon signature in the patient's peripheral blood mononuclear cells, which were also hypersensitive to stimulation by type I and type II interferons. The patient showed excellent clinical and functional laboratory response to tofacitinib, a Janus kinase inhibitor that disrupts interferon signaling. Our case highlights the need to utilize a multidisciplinary diagnostic approach and consider a comprehensive genetic evaluation for inborn errors of immunity in patients with an atypical immune-mediated thrombocytopenia phenotype.

BackgroundImmune-mediated lung injury and systemic hyperinflammation are characteristic of severe and critical coronavirus disease 2019 (COVID-19) in adults. Although the majority of severe acute respiratory syndrome coronavirus 2 infections in pediatric populations result in minimal or mild COVID-19 in the acute phase of infection, a small subset of children develop severe and even critical disease in this phase with concomitant inflammation that may benefit from immunomodulation. Therefore, guidance is needed regarding immunomodulatory therapies in the setting of acute pediatric COVID-19. This document does not provide guidance regarding the recently emergent multisystem inflammatory syndrome in children (MIS-C).MethodsA multidisciplinary panel of pediatric subspecialty physicians and pharmacists with expertise in infectious diseases, rheumatology, hematology/oncology, and critical care medicine was convened. Guidance statements were developed based on best available evidence and expert opinion.ResultsThe panel devised a framework for considering the use of immunomodulatory therapy based on an assessment of clinical disease severity and degree of multiorgan involvement combined with evidence of hyperinflammation. Additionally, the known rationale for consideration of each immunomodulatory approach and the associated risks and benefits was summarized.ConclusionsImmunomodulatory therapy is not recommended for the majority of pediatric patients, who typically develop mild or moderate COVID-19. For children with severe or critical illness, the use of immunomodulatory agents may be beneficial. The risks and benefits of such therapies are variable and should be evaluated on a case-by-case basis with input from appropriate specialty services. When available, the panel strongly favors immunomodulatory agent use within the context of clinical trials. The framework presented herein offers an approach to decision-making regarding immunomodulatory therapy for severe or critical pediatric COVID-19 and is informed by currently available data, while awaiting results of placebo-controlled randomized clinical trials.

Summary Background Data to inform surveillance and treatment for leukaemia predisposition syndromes are scarce and recommendations are largely based on expert opinion. This study aimed to investigate the clinical features and outcomes of patients with myelodysplastic syndrome or acute myeloid leukaemia and Shwachman-Diamond syndrome, an inherited bone marrow failure disorder with high risk of developing myeloid malignancies. Methods We did a multicentre, retrospective, cohort study in collaboration with the North American Shwachman-Diamond Syndrome Registry. We reviewed patient medical records from 17 centres in the USA and Canada. Patients with a genetic (biallelic mutations in the SBDS gene) or clinical diagnosis (cytopenias and pancreatic dysfunction) of Shwachman-Diamond syndrome who developed myelodysplastic syndrome or acute myeloid leukaemia were eligible without additional restriction. Medical records were reviewed between March 1, 2001, and Oct 5, 2017. Masked central review of bone marrow pathology was done if available to confirm leukaemia or myelodysplastic syndrome diagnosis. We describe the clinical features and overall survival of these patients. Findings We initially identified 37 patients with Shwachman-Diamond syndrome and myelodysplastic syndrome or acute myeloid leukaemia. 27 patients had samples available for central pathology review and were reclassified accordingly (central diagnosis concurred with local in 15 [56%] cases), 10 had no samples available and were classified based on the local review data, and 1 patient was excluded at this stage as not eligible. 36 patients were included in the analysis, of whom 10 (28%) initially presented with acute myeloid leukaemia and 26 (72%) initially presented with myelodysplastic syndrome. With a median follow-up of 4·9 years (IQR 3·9–8·4), median overall survival for patients with myelodysplastic syndrome was 7·7 years (95% CI 0·8–not reached) and 0·99 years (95% CI 0·2–2·4) for patients with acute myeloid leukaemia. Overall survival at 3 years was 11% (95% CI 1–39) for patients with leukaemia and 51% (29–68) for patients with myelodysplastic syndrome. Management and surveillance were variable. 18 (69%) of 26 patients with myelodysplastic syndrome received upfront therapy (14 haematopoietic stem cell transplantation and 4 chemotherapy), 4 (15%) patients received no treatment, 2 (8%) had unavailable data, and 2 (8%) progressed to acute myeloid leukaemia before receiving treatment. 12 patients received treatment for acute myeloid leukaemia—including the two patients initially diagnosed with myelodysplastic who progressed— two (16%) received HSCT as initial therapy and ten (83%) received chemotherapy with intent to proceed with HSCT. 33 (92%) of 36 patients (eight of ten with leukaemia and 25 of 26 with myelodysplastic syndrome) were known to have Shwachman-Diamond syndrome before development of a myeloid malignancy and could have been monitored with bone marrow surveillance. Bone marrow surveillance before myeloid malignancy diagnosis was done in three (33%) of nine patients with leukaemia for whom surveillance status was confirmed and 11 (46%) of 24 patients with myelodysplastic syndrome. Patients monitored had a 3-year overall survival of 62% (95% CI 32–82; n=14) compared with 28% (95% CI 10–50; n=19; p=0·13) without surveillance. Six (40%) of 15 patients with available longitudinal data developed myelodysplastic syndrome in the setting of stable blood counts. Interpretation Our results suggest that prognosis is poor for patients with Shwachman-Diamond syndrome and myelodysplastic syndrome or acute myeloid leukaemia owing to both therapy-resistant disease and treatment-related toxicities. Improved surveillance algorithms and risk stratification tools, studies of clonal evolution, and prospective trials are needed to inform effective prevention and treatment strategies for leukaemia predisposition in patients with Shwachman-Diamond syndrome. Funding National Institute of Health.

Given the ubiquity of leukopenia and sinopulmonary infections in childhood, differentiating patients with inborn errors of immunity (IEI) from otherwise healthy patients can be challenging. The diagnostic complexity is further exacerbated in disorders with wide phenotypic variability such as warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome. However, using a Sherlock approach with careful attention to details in the patient's medical history and physical examination coupled with a comprehensive family history can heighten the index of suspicion for underlying IEI. Subsequent iterative and deductive reasoning incorporating results from laboratory interrogation, response (or lack thereof) to standard therapy, and emergence of new symptoms can further aid in a timely diagnosis of IEI. Herein, we detail a WHIM syndrome kindred with marked phenotype variability, identified after the presentation of a child with intermittent neutropenia and sinopulmonary infections. The complexity of this kindred highlights the utility of an interspecialty, collaborative Sherlock approach to diagnosis, and care. In addition, the genetic underpinnings, diagnostic approaches, clinical features, supportive care options, and management of WHIM syndrome are reviewed.

As a key member of the innate and adaptive immune response, neutrophils provide insights into the hematopoietic and inflammatory manifestations of inborn errors of immunity (IEI) and the consequences of immunotherapy. The facile recognition of IEI presenting with neutropenia provides an avenue for hematologists to facilitate early diagnosis and expedite biologically rationale care. Moreover, enhancing the understanding of the molecular mechanisms driving neutropenia in IEI—decreased bone marrow reserves, diminished egress from the bone marrow, and decreased survival—offers an opportunity to further dissect the pathophysiology driving neutropenia secondary to iatrogenic immune dysregulation, eg, immune checkpoint inhibitors and chimeric antigen receptor T-cell therapy.

Optimal management of patients with combined immunodeficiency, especially pertaining to hematopoietic stem cell transplantation (HSCT), remains unclear.To identify factors influencing HSCT and mortality in the population with combined immunodeficiency in North America.We identified 337 participants in the United States Immunodeficiency Network database with diverse forms of combined immunodeficiency and their characteristics, including demographic characteristics, laboratory values, infectious history, comorbidities, and treatment strategies. Univariate analysis was performed using logistic regression, whereas multivariate analysis was performed using multiple Cox proportional hazards.On univariate analysis, disseminated invasive viral infections and variants in STAT3, GATA2, and, DOCK8 were associated with increased odds of HSCT. Mucocutaneous fungal infections and variants in STAT3 were associated with increased odds of survival, whereas disseminated/invasive fungal infections, disseminated/invasive viral infections, and parasitic infections were associated with decreased odds of survival. On multiple variable Cox proportional hazards analysis, variants in ZAP70, nonspecific bacterial, and disseminated/invasive viral infections were associated with increased hazards of transplantation, whereas variants in multiple genes (RMRP, NEMO, DOCK8, CD40L, and CARD9), disseminated/invasive viral infections, autoimmune disease, and higher absolute lymphocyte count were associated with increased hazards of death. Importantly, demographic characteristics, basic lymphocyte subset counts, and absence of genetic diagnosis were not associated with HSCT or mortality.We determined that specific genetic diagnoses and infection burden impacts the decision to undergo HSCT in this cohort. In addition, certain genetic diagnoses and invasive viral infections carry an increased risk of mortality.

Histiocytic neoplasms are rare hematologic disorders accounting for less than 1% of cancers of the soft tissue and lymph nodes. Clinical presentation and prognosis of these disorders can be highly variable, leading to challenges for diagnosis and optimal management of these patients. Treatment often consists of systemic therapy, and recent studies support use of targeted therapies for patients with these disorders. Observation (“watch and wait”) may be sufficient for select patients with mild disease. These NCCN Guidelines for Histiocytic Neoplasms include recommendations for diagnosis and treatment of adults with the most common histiocytic disorders: Langerhans cell histiocytosis, Erdheim-Chester disease, and Rosai-Dorfman disease.

Both profound neutropenia and functional phagocyte disorders render patients susceptible to recurrent, unusual, and/or life-threatening infections. Many disorders also have nonhematologic manifestations and a substantial risk of leukemogenesis. Diagnosis relies on clinical suspicion and interrogation of the complete blood count with differential/bone marrow examination coupled with immunologic and genetic analyses. Treatment of the quantitative neutrophil disorders depends on granulocyte colony-stimulating factor, whereas management of functional phagocyte disease is reliant on antimicrobials and/or targeted therapies. Hematopoietic stem cell transplant remains the only curative option for most disorders but is not used on a routine basis.

While the COVID-19 pandemic triggered numerous clinical practice changes and resulted in severe consequences either directly or indirectly for select pediatric patients, important lessons were learned, and there are silver linings for immunocompromised children evident among the chaos. At a minimum, the pandemic raised global awareness of infection risk, viral transmissibility, and the immune system. Handwashing, comprehensive disinfection practices of shared surfaces, and mask wearing are more normalized. School shutdowns during the COVID-19 pandemic not only kept children from exposure to SARS-CoV-2 but also decreased the incidence of pneumonia, otitis media, streptococcal pharyngitis, urinary tract infections, croup, gastrointestinal infections, and asthma.104 Strategies to mitigate SARS-CoV-2 infection including ventilation upgrades and cohorting methods are likely to help attenuate infectious exposures as students return to the classroom. In addition, the broad acceptance of virtual learning and incorporation of virtual learners in a hybrid classroom are practices expected to be of value to immunodeficient patients. Beyond schooling, the creative transition of other activities, for example, dance, karate, and enrichment opportunities, for example, art classes and streaming concerts, has allowed immunocompromised children to participate with their peers. As risk of SARS-CoV-2 transmission lessens, immunocompetent children will return to school and other in-person activities; the expanded services offered during the pandemic need to be continued for children with weakened immune systems. From a health care perspective, the massive uptake of telemedicine provided an alternative strategy for patients with compromised immune systems to maintain access to care with increased convenience and decreased cost. Given that immunocompromised patients are likely to benefit from continued telehealth options after the pandemic, it is imperative that action be taken to preserve the expansion of compensated telehealth options, while also appreciating that in-person visits are vital for some patients to diagnose new or progressive disease. In addition, strategies to mitigate barriers for telehealth uptake to improve equity of access as well as parental/patient preferences for care received in-person versus virtually must be explored. Although global efforts have accelerated our understanding and care of SARS-CoV-2 patients, our knowledge of clinical outcomes and treatment in immunocompromised patients is limited, particularly in inborn errors of immunity and pediatric HIV. Challenges remaining for pediatricians include sustained, global collaboration to consolidate knowledge in these rare patient groups, continued adaptation of knowledge gained from immunocompetent patients to immunocompromised cohorts, and further study on the safety and efficacy of current and developing vaccines. Persistent advocacy for rare diseases is even more critical as the clinical, scientific, and philanthropic communities remain focused on COVID-19 care and research. Finally, a comment that immunocompromised parents hear is, “I finally understand what it is like to live like you. I am afraid to get an infection. I cannot just go anywhere I want to go anymore”. Although the COVID-19 pandemic has been difficult for everyone on a personal and professional level, the anxiety of infection and social isolation will persist for immunocompromised families even as the risk of SARS-CoV-2 transmission subsides. It is imperative that we leverage knowledge gained from this pandemic to improve the health and quality of life of immunocompromised children so that they may live without fear.

Hemophagocytic lymphohistiocytosis (HLH) is an immune dysregulatory syndrome characterized by severe inflammation and end-organ damage. Due to significant organ dysfunction, patients often require extracorporeal membrane oxygenation (ECMO) and continuous renal replacement therapy (CRRT). In this report, we describe consideration for adjusting treatment in the context of extracorporeal organ support. We describe agents commonly used and dosing adjustments made in light of extracorporeal organ support. We report six cases that illustrate the feasibility of initiating standard HLH therapies in patients requiring these modalities.

To understand the mechanisms that mediate germline genetic leukemia predisposition, we studied the inherited ribosomopathy Shwachman-Diamond syndrome (SDS), a bone marrow failure disorder with high risk of myeloid malignancies at an early age. To define the mechanistic basis of clonal hematopoiesis in SDS, we investigate somatic mutations acquired by patients with SDS followed longitudinally. Here we report that multiple independent somatic hematopoietic clones arise early in life, most commonly harboring heterozygous mutations in EIF6 or TP53. We show that germline SBDS deficiency establishes a fitness constraint that drives selection of somatic clones via two distinct mechanisms with different clinical consequences. EIF6 inactivation mediates a compensatory pathway with limited leukemic potential by ameliorating the underlying SDS ribosome defect and enhancing clone fitness. TP53 mutations define a maladaptive pathway with enhanced leukemic potential by inactivating tumor suppressor checkpoints without correcting the ribosome defect. Subsequent development of leukemia was associated with acquisition of biallelic TP53 alterations. These results mechanistically link leukemia predisposition to germline genetic constraints on cellular fitness, and provide a rational framework for clinical surveillance strategies., Understanding the molecular basis of leukaemia predisposition is essential for intervention. The authors here investigate germline genetic leukaemia predisposition by studying Shwachman-Diamond syndrome and report compensatory inactivating mutations in EIF6 and transforming biallelic TP53 alterations.

Congenital conditions caused by an absolute or functional deficiency of neutrophils are associated with considerable morbidity and mortality in children and adults. These disorders manifest with various phenotypes, but all contribute to an elevated risk of serious bacterial, fungal, and even viral infections. Quantitative neutrophil disorders include severe congenital neutropenia, cyclic neutropenia, and bone marrow failure syndromes, most notably Shwachman-Diamond syndrome. Phagocyte functional deficits result from myeloperoxidase deficiency; failed oxidative burst, e.g., chronic granulomatous disease; flawed migration as seen in the leukocyte adhesion disorders; and difficulty with intracellular granules as in Chediak-Higashi syndrome and neutrophil-specific granule deficiency. Early diagnosis is essential to minimizing the morbidity and mortality of these conditions with crucial diagnostic laboratory analyses including functional neutrophil studies to assess neutrophil migration and oxidative burst capabilities, flow cytometry, and direct pathologic evaluation of the bone marrow and peripheral blood. Supportive care often entails usage of antimicrobial prophylaxis, aggressive management of infectious complications, and regular administration of G-CSF. Frequently hematopoietic stem cell transplantation can be curative but is not without risks.

Background Diamond-Blackfan anemia (DBA) is an inherited bone marrow failure syndrome characterized by anemia, short stature, congenital anomalies, and cancer predisposition. Most cases are due to mutations in genes encoding ribosomal proteins (RP) leading to RP haploinsufficiency. Effective treatments for the anemia of DBA include chronic red cell transfusions, long-term corticosteroid therapy, or hematopoietic stem cell transplantation. In a small patient series and in animal models, there have been hematologic responses to L-leucine with amelioration of anemia. The study objectives of this clinical trial were to determine feasibility, safety, and efficacy of L-leucine in transfusion-dependent patients with DBA. Procedure Patients ≥2 years of age received L-leucine 700 mg/m2 orally three times daily for nine months to determine a hematologic response and any improvement in growth (NCT01362595). Results This multicenter, phase I/II study enrolled 55 subjects; 43 were evaluable. There were 21 males; the median age at enrollment was 10.4 years (range, 2.5-46.1 years). No significant adverse events were attributable to L-leucine. Two subjects had a complete erythroid response and five had a partial response. Nine of 25, and 11 of 25, subjects experienced a positive weight and height percentile change, respectively, at the end of therapy. Conclusions L-leucine is safe, resulted in an erythroid response in 16% of subjects with DBA, and led to an increase in weight and linear growth velocity in 36% and 44% of evaluable subjects, respectively. Further studies will be critical to understand the role of L-leucine in the management of patients with DBA.

Quality of life (QOL) and patient-reported outcomes (PROs) assessments in immunodeficiency patients, including those with chronic severe neutropenia conditions, are imperative to determining modifiable health-related features to optimize care. We present the largest study to date of QOL in those with chronic severe neutropenia conditions with further evaluation of patient provider satisfaction and patient-reported outcome measures. Subjects completed electronic surveys assessing QOL, PROs, and patient provider satisfaction. There is a significantly negative impact of a chronic severe neutropenia disorder on QOL, fatigue, physical function, cognitive function and pain in adult patients when compared to controls. Children with a chronic neutropenia condition had comparable QOL to controls, but reported fewer depressive symptoms, improved mobility, and stronger self-reported peer relationships. Adults had worse scores for QOL, depression and fatigue when compared to children. Adult and pediatric chronic severe neutropenia patients or their caregivers felt that their medical provider was compassionate, trustworthy, and accessible. However, less than 50% of adult patients agreed their clinician had excellent expertise in white blood cell disorders. Chronic neutropenia complexly affect QOL and PROs. An analysis of these parameters allows for targeted interventions to improve patient psychosocial, physical and neurocognitive health.

Expanding Clinical Spectrum of Female X-linked Lymphoproliferative Syndrome 2Shruthi Suryaprakash, MD1, Mohammad El-Baba2, MD, Kelly J. Walkovich, MD3, Sureyya Savasan, MD41Children’s Hospital of Michigan2Division of Gastroenterology, Children’s Hospital of Michigan3Division of Hematology/Oncology, Immuno-Hematology Comprehensive Program, C.S. Mott Children’s Hospital, University of Michigan4Division of Hematology/Oncology and Blood and Marrow Transplant Program, Children’s Hospital of Michigan, Carman and Ann Adams Department of Pediatrics, Barbara Ann Karmanos Cancer Center, Central Michigan University College of MedicineCorrespondence: Sureyya Savasan, MD3901 Beaubien Blvd.Division of Hematology/OncologyBlood and Marrow Transplant ProgramChildren’s Hospital of MichiganDetroit, Michigan 48201E-mail: savas1s@cmich.eduPhone: 313-745-5516 Fax: 313-745-5237Text word count: 495Reference count: 4Tables and figures: 1Short running title: Spectrum of Symptomatic Female XLP2Key words: Female XLP2, EBV reactivation, Vitamin B12 deficiency, B-cell lymphopenia, clonal T-LGL proliferationDear Editor:X-linked lymphoproliferative syndrome type 2 (XLP2) due to pathogenic variants in the X-linked inhibitor of apoptosis (XIAP) gene is a rare cause of primary immunodeficiency. Symptomatic patients, primarily males, present with hemophagocytic lymphohistiocytosis (HLH), inflammatory bowel disease (IBD) and/or transient hypogammaglobinaemia.1 However, XLP2 in female patients is complicated with the rarity of symptomatic cases and clinical heterogeneity.2 We report a female affected by XLP2 with previously unreported findings.A currently 18-year-old female presented with fever, abdominal pain, diffuse lymphadenopathy, splenomegaly, and pancytopenia three years ago. She was diagnosed with HLH, treated with steroids and found to have low B-cells and borderline hypogammaglobinemia. Additionally, a single pathogenic variant in XIAP (c.389_392delACAG [p.Asp130Glyfs*11]) was identified. Further workup showed presence of EBV IgG, and normal expression of XIAP protein in only 8-19% of various white blood cell types by flow cytometry indicating skewed X chromosome inactivation. She had intermittent infections, one resulting in an additional HLH flare with elevated IL-18 and CXCL9 levels that was treated with steroids and intravenous immunoglobulin (IVIG). Repeated EBV PCR testing had been negative.However, she was found to have EBV reactivation with positive EBV VCA-IgM, high titer VCA-IgG and EA-IgG levels while EBV-PCR was negative when she presented to our clinic with diarrhea. There was ongoing history of headaches, abdominal pain, joint pain, and ADHD at that time. Later, she underwent work up for recurrent abdominal pain, diarrhea, urgency and elevated fecal calprotectin. MRI-enterography and capsule endoscopy were negative. Endoscopy was remarkable for chronic active proctitis. She was prescribed mesalamine with significant improvement in abdominal pain and resolution of mucuosy stools.Due to persistent knee/ankle pain, she was investigated for peripheral neuropathy and was found to have low vitamin B12 levels (112-145pg/mL; N:180-914) without dietary restrictions, absent anti-intrinsic factor antibodies and negative family history. Her pain improved significantly on vitamin B12 injections and gabapentin with normalization of vitamin B12 levels.She continued to have fluctuating and borderline low levels of serum immunoglobulins with persistently low B-cells. She was given IVIG supplementation when serum IgG levels were low. No additional HLH flares have occurred. Mild increase in CD5-dim T-cells (9%) representing T-large granular lymphocytes (T-LGL) and clonal T-cell receptor (TCR) rearrangement pattern were identified in peripheral blood. She continues to have migraine episodes and very high EA-IgG at >150U/mL (N

Shwachman-Diamond syndrome (SDS) is an inherited bone marrow failure syndrome with predisposition to developing leukemia. We found that multiple independent somatic hematopoietic clones arise early in life, most commonly harboring heterozygous mutations inEIF6orTP53.EIF6mutations cause functional compensation for the germline deficiency by alleviating the SDS ribosome joining defect, improving translation, and reducing p53 activation.TP53mutations decrease checkpoint activation without affecting ribosome assembly. We link development of leukemia with acquisition of biallelicTP53alterations. Our results define distinct pathways of clonal selection driven by germline fitness constraint and provide a mechanistic framework for clinical surveillance.

Expanding Clinical Spectrum of Female X-linked Lymphoproliferative Syndrome 2Shruthi Suryaprakash, MD1, Mohammad El-Baba2, MD, Kelly J. Walkovich, MD3, Sureyya Savasan, MD41Children’s Hospital of Michigan2Division of Gastroenterology, Children’s Hospital of Michigan3Division of Hematology/Oncology, Immuno-Hematology Comprehensive Program, C.S. Mott Children’s Hospital, University of Michigan4Division of Hematology/Oncology and Blood and Marrow Transplant Program, Children’s Hospital of Michigan, Carman and Ann Adams Department of Pediatrics, Barbara Ann Karmanos Cancer Center, Central Michigan University College of MedicineCorrespondence: Sureyya Savasan, MD3901 Beaubien Blvd.Division of Hematology/OncologyBlood and Marrow Transplant ProgramChildren’s Hospital of MichiganDetroit, Michigan 48201E-mail: savas1s@cmich.eduPhone: 313-745-5516 Fax: 313-745-5237Text word count: 495Reference count: 4Tables and figures: 1Short running title: Spectrum of Symptomatic Female XLP2Key words: Female XLP2, EBV reactivation, Vitamin B12 deficiency, B-cell lymphopenia, clonal T-LGL proliferationDear Editor:X-linked lymphoproliferative syndrome type 2 (XLP2) due to pathogenic variants in the X-linked inhibitor of apoptosis (XIAP) gene is a rare cause of primary immunodeficiency. Symptomatic patients, primarily males, present with hemophagocytic lymphohistiocytosis (HLH), inflammatory bowel disease (IBD) and/or transient hypogammaglobinaemia.1 However, XLP2 in female patients is complicated with the rarity of symptomatic cases and clinical heterogeneity.2 We report a female affected by XLP2 with previously unreported findings.A currently 18-year-old female presented with fever, abdominal pain, diffuse lymphadenopathy, splenomegaly, and pancytopenia three years ago. She was diagnosed with HLH, treated with steroids and found to have low B-cells and borderline hypogammaglobinemia. Additionally, a single pathogenic variant in XIAP (c.389_392delACAG [p.Asp130Glyfs*11]) was identified. Further workup showed presence of EBV IgG, and normal expression of XIAP protein in only 8-19% of various white blood cell types by flow cytometry indicating skewed X chromosome inactivation. She had intermittent infections, one resulting in an additional HLH flare with elevated IL-18 and CXCL9 levels that was treated with steroids and intravenous immunoglobulin (IVIG). Repeated EBV PCR testing had been negative.However, she was found to have EBV reactivation with positive EBV VCA-IgM, high titer VCA-IgG and EA-IgG levels while EBV-PCR was negative when she presented to our clinic with diarrhea. There was ongoing history of headaches, abdominal pain, joint pain, and ADHD at that time. Later, she underwent work up for recurrent abdominal pain, diarrhea, urgency and elevated fecal calprotectin. MRI-enterography and capsule endoscopy were negative. Endoscopy was remarkable for chronic active proctitis. She was prescribed mesalamine with significant improvement in abdominal pain and resolution of mucuosy stools.Due to persistent knee/ankle pain, she was investigated for peripheral neuropathy and was found to have low vitamin B12 levels (112-145pg/mL; N:180-914) without dietary restrictions, absent anti-intrinsic factor antibodies and negative family history. Her pain improved significantly on vitamin B12 injections and gabapentin with normalization of vitamin B12 levels.She continued to have fluctuating and borderline low levels of serum immunoglobulins with persistently low B-cells. She was given IVIG supplementation when serum IgG levels were low. No additional HLH flares have occurred. Mild increase in CD5-dim T-cells (9%) representing T-large granular lymphocytes (T-LGL) and clonal T-cell receptor (TCR) rearrangement pattern were identified in peripheral blood. She continues to have migraine episodes and very high EA-IgG at >150U/mL (N

Pediatric thrombocytopenia has a wide differential diagnosis, and recently, genetic testing to identify its etiology has become more common. We present a case of a 16-year-old boy with a history of chronic moderate thrombocytopenia, who later developed constitutional symptoms and bilateral hand edema with cold exposure. Laboratory evaluation revealed evidence both of inflammation and elevated muscle enzymes. These abnormalities persisted over months. His thrombocytopenia was determined to be immune mediated. Imaging revealed lymphadenopathy and asplenia, and a muscle biopsy was consistent with tubular aggregate myopathy. Ophthalmology evaluation noted photosensitivity, pupillary miosis, and iris hypoplasia. Genetic testing demonstrated a pathogenic variant in STIM1 consistent with autosomal dominant Stormorken syndrome. Our case is novel because of the overlap of phenotypes ascribed to both gain-of-function and loss-of-function pathogenic variants in STIM1, thereby blurring the distinctions between these previously described syndromes. Pediatricians should consider checking muscle enzymes when patients present with thrombocytopenia and arthralgia, myalgia, and/or muscle weakness. Our case highlights the importance of both multidisciplinary care and genetic testing in cases of chronic unexplained thrombocytopenia. By understanding the underlying genetic mechanism to a patient’s thrombocytopenia, providers are better equipped to make more precise medical management recommendations.

Background: Acquired generalized lipodystrophy (AGL) is characterized by near-total fat loss that develops after birth. Although the molecular pathogenesis of AGL is unclear, there is a link to autoimmunity and inflammation. Notably, the panniculitis associated variety of AGL may present with subcutaneous inflammatory nodules that ultimately progress to generalized fat loss. Here, we report on a complex patient with AGL in whom whole-exome sequencing (WES) identified several pathogenic variants and variants of uncertain significance (VUS) that encourage us to think about AGL more broadly. Clinical Case: This is a 38-year-old male who was first diagnosed with juvenile rheumatoid arthritis at age 2, after being evaluated for delayed ability to ambulate. At that time, he was also diagnosed with Weber-Christian disease following a skin biopsy due to the suspicion of panniculitis. Over time, he progressively lost body fat throughout the body and developed hypertriglyceridemia, hypertension, and nephropathy leading to the diagnosis of AGL. At age 10, he was diagnosed with type 1 diabetes mellitus, and at age 14, with autoimmune hepatitis. Due to the tightening of his hands, calf pain, and increased CPK levels, a muscle biopsy was performed, suggesting polymyositis. He had been treated with azathioprine and steroids, which were discontinued at age 26, after a liver biopsy that showed grade 2 fibrosis. Further, he was diagnosed with non-ischemic dilated cardiomyopathy (DCM), evolving with atrial fibrillation with a rapid ventricular response and complicated with left atrial appendage thrombus. Of interest, his mother and two maternal aunts had been diagnosed with atrial fibrillation. One of his maternal uncles presented non-ischemic cardiomyopathy and an early sudden cardiac arrest. His mother also had mitochondrial myopathy, and his father had type 2 diabetes mellitus and IgG deficiency. WES identified three different variants: a maternally inherited pathogenic variant in TTN (c.88473_88477delAGCTT; p.W29493X) associated with DCM, a paternally inherited pathogenic variant in TNFRSF13B (c.310T>C; p.C104R) associated with CVID/IgA deficiency, and a maternally inherited variant of uncertain clinical significance in NLRP3 (c.1469G>A; p.R490K). Although the frequency of this variant was relatively high, several variants in the NLRP3 gene have been previously associated with inflammasomopathy. Conclusion: This case highlights challenging presentations of AGL and the complexity of the disease. As we are yet beginning to understand the molecular mechanisms behind the so-called “acquired fat loss” and its relation to inflammatory and complex immune system diseases, further efforts are critical to better recognize different AGL phenotypes and phenotype-genotype correlations. Additional efforts should be placed on WES for AGL patients and functional validation of identified VUSs.

Nonimmune hydrops remains a challenge in the prenatal setting with many cases not having a clear etiology determined prior to birth. We present an unusual case of one fetus of a dichorionic twin pair presenting at 24 weeks’ gestation with hydrops and fetal pancytopenia with complete absence of white cells of unknown etiology, as revealed by cordocentesis. Serial red blood cell transfusions resulted in resolution of hydrops and continuation of the pregnancy until 35 weeks’ gestation. Pancytopenia was noted throughout gestation and persisted in the newborn period. Moreover, the T-cell receptor excision circle (TREC) assay, a newborn screening test for severe T-cell deficiency, was abnormal at birth. Further evaluation revealed detectable TRECs and normal response to lymphocyte mitogens indicating some preserved thymic and lymphocyte function. The affected child had spontaneous resolution of the pancytopenia, including her severe T-cell deficiency, by 10 weeks of life. There has been no recurrence as of 24 months of age. The self-resolving nature of the pancytopenia is an important feature of this case of nonimmune hydrops. The abnormal TREC assay at birth in the affected infant may help explain the discordant prenatal findings.

Acquired generalized lipodystrophy (AGL) is characterized by extensive adipose tissue loss, subsequent development of metabolic disease with severe insulin resistance and hypertriglyceridemia and a varying spectrum of autoimmune or immune-dysregulatory features. We recently evaluated twelve patients (8 females, 4 males; age range: 14 - 54 years). The reported onset of fat loss varies from age 2 to 31 years of age but most patients presenting between age 3 and 19 years. The age of diagnosis varies from 4 to 53 years. Clinical panniculitis was reported in 4 patients. Although adipose tissue loss occurred in a generalized fashion, several patients had measured body fat as high as 35 percent on DEXA scans with leptinemia also covering a spectrum from undetectable levels to as high as 6.2 ng/ml. All patients had insulin resistance. Eight patients had diabetes (4 had type 1 diabetes). Dyslipidemia was diagnosed in 11 patients. Hepatic steatosis and/or elevated liver function tests were detected in all subjects. The liver disease was varied and had distinctive characteristics of episodic increases in liver tests in 4 with development of portal hypertension and splenomegaly. These patients had periportal lymphocytic and eosinophilic infiltration on liver biopsies when undertaken during transaminitis and developed portal hypertension, splenomegaly and biliary obstruction while preserving synthetic liver function over time, suggesting that their clinical course may be consistent with nodular regenerative hyperplasia (NRH). Patients also developed a wide range of immune-dysregulatory features including IgA deficiency, common variable immunodeficiency, autoimmune hives, angioedema, eczematous dermatitis, autoimmune hypothyroidism, Graves’ disease, atrophic gastritis, juvenile dermatomyositis, rheumatoid arthritis, polyarthritis, immune thrombocytopenia, cutaneous morphea, lentigo, peripheral T cell lymphoma, graft versus host disease, hemophagocytic syndrome, interstitial lung disease, autoimmune hemolytic anemia, autoimmune colitis, Crohn disease, and periodic fevers. Low complement 4 levels were detected in 5 patients, and 3 had low complement 3 levels. Genetic workup revealed CTLA-4 haploinsufficiency in one case and variants of uncertain significance in P4HA3, TTN, TNFRSF13B, and NLRP3 genes in several others. One distinctive patient was heterozygous for a pathogenic LRBA variant. The exact etiology of AGL is unknown and heterogeneity creates a diagnostic challenge. While panniculitis is a distinct initial presentation in some cases, immune dysregulation affecting multiple organs with accompanying NRH may constitute a new subgroup of AGL. Immune check-point perturbation via gremlin mutation may also lead to AGL. Collective review of cases with predetermined clinical and laboratory evaluation criteria may be helpful to describe subgroups of AGL.

Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a rare, life-threatening hyperinflammatory syndrome characterized by overactivation of the immune system due to systemic release of proinflammatory cytokines, especially of interferon gamma (IFNγ), and persistent activation of macrophages/histiocytes and T cells. Emapalumab, a fully human, anti-IFNγ monoclonal antibody that binds to both free and receptor-bound IFNy, neutralizing its biologic activity, was approved by the Food and Drug Administration (FDA) in 2018 for the treatment of adult and pediatric patients with primary HLH with refractory, recurrent or progressive disease or intolerance with conventional HLH therapy. The safety and efficacy of emapalumab was based on results from a pivotal phase 2/3 trial which reported a 63% overall response in patients treated with emapalumab. Since approval, no study has evaluated the use of emapalumab in a larger cohort of patients in the real-world clinical setting. Aim: To assess real-world treatment patterns and outcomes, clinical and demographic characteristics among patients treated with emapalumab. Method: This retrospective, non-interventional, observational medical chart review study will include patients treated across treatment centers in the US with emapalumab in a non-clinical trial setting. The study aims to include more than 100 patients who have been treated with at least one dose of emapalumab between November 20, 2018 and December 31, 2020 (patient identification period). The date that the patient initiates treatment with emapalumab within the patient identification period is defined as the index date. The post-index date is defined as the period from the index date through to the study end date (June 30, 2021), end of data availability for the patient, or date of death, whichever occurs first. Patients will be classified into three groups (i.e. primary HLH, secondary HLH, or non-HLH) based on the information obtained from their charts, the HLH 2004 diagnostic criteria, and adjudication by the REAL-HLH Steering Committee. Results: The primary objective of the study is to describe treatment patterns in patients with HLH treated with emapalumab in a real-world clinical setting, including emapalumab dose, treatment duration, and reasons for initiating or discontinuing treatment. The secondary objectives are to describe demographic and clinical characteristics of patients with HLH treated with emapalumab, and their outcomes. The exploratory objectives include detailing the demographic, clinical characteristics, treatment patterns, and outcomes of patients with non-HLH clinical conditions treated with emapalumab (Table 1). Demographics and clinical characteristics will be analyzed at the time of diagnosis. Treatment patterns and outcomes will be analyzed during the post-index date. Conclusion: The study aims to assess treatment patterns and outcomes, clinical and demographic characteristics among patients treated with emapalumab, a novel IFNγ blocking agent, in real-world clinical settings in the US. Figure 1 Figure 1. Disclosures Allen: Sobi: Consultancy. Leiding: Sobi: Consultancy. Chandrakasan: Sobi: Consultancy. Walkovich: X4 Pharmaceuticals: Other: Local PI for clinical trial involving mavorixafor and patients with neutropenia; Swedish Orphan Biovitrum AB (Sobi): Consultancy, Honoraria; Pharming: Honoraria, Membership on an entity's Board of Directors or advisory committees; Horizon Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees. Oladapo: Sobi: Current Employment. Yee: Sobi: Current Employment. Pednekar: Sobi: Consultancy; PRECISIONheor: Current Employment. Raza: Sobi: Consultancy; PRECISIONheor: Current Employment. Jordan: Sobi: Consultancy.

BACKGROUND: Immune thrombocytopenia purpura (ITP) has a complex pathogenesis and may be a primary diagnosis or secondary to an underlying condition 1. Evaluation for underlying diagnoses in patients presenting with atypical features of classic ITP is key, as this can impact treatment decisions, therapy response, and prognosis. Genetic variants that predispose patients to ITP are especially important to investigate as patients may be at risk for additional autoimmune phenomenon or malignancy. The SARS CoV-2 pandemic has added further complexity as reports suggest the infection can lead to autoimmunity in those with genetic predispositions 2,3. Loss of the suppressor of cytokine signaling 1 (SOCS1) function has been described to manifest with autoinflammatory syndrome, with or without immunodeficiency 4,5. Reports of autoimmunity developing in patients with SOCS1 haploinsufficiency after SARS CoV-2 infection are documented, including multi-system inflammatory syndrome (MIS-C) 2. A proposed mechanism of this virus-triggered autoimmunity includes a transient innate and adaptive immunodeficiency 3. This raises the question whether patients harboring genetic variants with risk of autoimmunity are placed at an even higher risk for ITP in the wake of SARS-CoV2 infection. CASE PRESENTATION: We present a 6-year-old female with isolated thrombocytopenia of 4,000/uL identified during evaluation for severe arthralgias unresponsive to corticosteroid treatment (maximum dose 1mg/kg/day) over a 6-month period. Laboratory results at presentation were consistent with ITP, including presence of platelet autoantibodies. Evaluation revealed hypocellularity for age (~50%) on bone marrow evaluation as well as elevated IgE (2080 kU/L), with IgA, IgM, and IgG levels within reference range. She had a remote history of SARS CoV-2-like illness and SARS CoV-2 antibodies were found present in serologic assay, without a history of vaccination. Genetic testing, including chromosomal microarray from peripheral blood and marrow, was included in the diagnostic workup given concern for a history of developmental delays with macrocephaly and necessity to rule-out malignancy with the patient noted to have a 5 mega-base deletion at 16p13.2p13.11, which includes the SOCS1 gene. Comprehensive next generation sequencing for additional immune dysregulation/primary immunodeficiency associated variants was unremarkable. Functional studies of surface expression of interferon-inducible genes (CD169 (SIGLEC-1)) and STAT1 phosphorylation via analysis of CD14+ monocytes revealed excess interferon signaling previously described in patients with SOCS1 haploinsufficiency (Figure 1). Measurements of B-cell-activating factor were also found to be extremely elevated at 6432 pg/mL. The patient's ITP course was complicated by hematuria, melena and refractory platelet response to first line therapy consisting of intravenous immunoglobulin 1 g/kg x2 doses and 2 mg/kg/day prednisolone. She required escalation to high dose methylprednisolone (30mg/kg), rituximab 375 mg/m 2/weekly x4 doses, and concurrent romiplostim (2 doses) for control of thrombocytopenia and bleeding manifestations. Her rheumatologic symptoms subsided with initiation of corticosteroids, and she has subsequently completed a prolonged corticosteroid taper. She currently has a normal platelet count with non-steroidal anti-inflammatory therapy utilized for arthralgia management with plan to transition to JAK inhibition for maintenance therapy. CONCLUSION: This case highlights the potential impact of investigating for susceptibility genes for ITP with consideration for broader testing including targeted next generation sequencing panels or microarray analysis in patients with atypical ITP presentations or response to therapy, as knowledge of this patient's underlying genetics led to earlier treatment and use of alternative agents. Additionally, the case adds the novel finding of bone marrow hypocellularity to the clinical phenotype of SOCS1 haploinsufficiency, as this has not yet been reported and contributes to the literature on the relationship of autoimmunity and SARS CoV-2 infections in patients with predisposing genetic variants. Figure 1 Figure 1. Disclosures Walkovich: Horizon Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees; Pharming: Honoraria, Membership on an entity's Board of Directors or advisory committees; Swedish Orphan Biovitrum AB (Sobi): Consultancy, Honoraria; X4 Pharmaceuticals: Other: Local PI for clinical trial involving mavorixafor and patients with neutropenia.

Background Hemophagocytic lymphohistiocytosis (HLH) is an increasingly recognized life-threatening syndrome characterized by excessive inflammation and immune dysregulation. However, little is known about HLH presenting in neonates. Methods To describe the phenotype, etiology, and efficacy of therapy for infants presenting within 28 days of birth and diagnosed with HLH prior to 90 days of life, a retrospective multi-center study was conducted identifying 13 previously unreported cases from 8 centers. A systematic literature review identified 58 additional cases that were sufficiently similar to allow pooling for meta-analysis (n=71). Results Presenting symptoms and laboratory findings of HLH were non-specific and indistinguishable from other neonatal critical illnesses. More than 85% of patients demonstrated hepatomegaly, splenomegaly, hyperferritinemia, transaminitis, hypoalbuminemia, and severe thrombocytopenia. Notably, liver dysfunction appears more common in neonatal HLH compared to published reviews of HLH cases across the age spectrum. Genetic testing was pursued in 60% of the cohort with pathogenic variants identified in a third of patients (PRF1 in 15, UNC13D in 8). Ten additional cases occurred with a family history of HLH, for a total of 46% (33/71) of cases of presumed familial HLH. Seventeen cases (24%) represented secondary HLH with an identified trigger for immune dysregulation (e.g. infection or non-HLH disease) in the absence of an HLH-associated genetic mutation or family history. Twenty-one (30%) neonatal HLH cases were of unknown etiology. Two-year survival from presentation was low at 27%, with a trend toward superior 2-year overall survival for those with secondary HLH at 65% (unknown etiology 21%, familial HLH 18%, p=0.06; Figure). Ten patients (n=6 familial HLH, n=4 unknown etiology) underwent allogeneic hematopoietic cell transplantation (HCT) at a median of 4.8 months of age. HCT was associated with improved 2-year overall survival (OS) from HLH diagnosis (78% with HCT versus 11% without HCT, p Conclusion Liver dysfunction in a severely ill neonate should prompt consideration of HLH as an etiology. Our study supports consideration of HCT for any neonate with HLH, except those with an identified trigger and absence of an HLH-associated gene mutation prompting classification as secondary HLH. Early lethality combined with superior HCT outcomes when HLH is well-controlled additionally highlight the need for novel HLH therapies to bridge to HCT. Further studies to better elucidate details of pre-HCT therapy, HCT conditioning regimens and how best to navigate multi-organ failure at HLH presentation are needed. Figure Disclosures No relevant conflicts of interest to declare.

Background: Shwachman-Diamond Syndrome (SDS) is a bone marrow failure disorder caused by impaired removal of EIF6 from the nascent 60S ribosome subunit, resulting in defective ribosome assembly. SDS patients have a high risk of myeloid neoplasms (MN) and the prognosis of those that develop MN is poor. Knowledge of the kinetics and functional consequences of somatic mutation acquisition in SDS may offer insight into mechanism of transformation and the potential for therapuetic intervention. Methods: We performed whole exome sequencing of 45 samples from 30 patients, and validated recurrent somatically mutated genes using targeted sequencing with error suppression in prospectively collected samples from 110 patients in the North American SDS Registry. We correlated mutation status with clinical outcome and performed functional studies to understand the consequence of somatic mutations in SDS. Results: We detected somatic mutations in 74 of 98 (76%) patients with germline biallelic SBDS mutations (median 2 mutations/patient, range 0-21). We found no mutations in patients with SDS-like disease; those who have clinical features of SDS without disease defining mutations. Of the 83 patients with SDS without a MN diagnosis, 60 (72%) had detectable clonal hematopoiesis (CH), 40 of whom had more than one mutation (median 3, range 1-21). The most frequently mutated genes were EIF6 (60/98, 61%),TP53 (44/98, 45%), PRPF8 (12/98, 12%), and CSNK1A1 (6/98, 6%). Among SDS patients with TP53 mutated CH, 90.9% (30 of 33) had concurrent EIF6 mutations. To determine whether EIF6 and TP53 mutations occur in the same or different clones, we performed single cell DNA sequencing. Among the 47 clones identified with either EIF6 or TP53 mutations, 24 had a sole EIF6 mutation, and 21 had a sole TP53 mutation, showing that these mutations arise in separate clones. To study the functional consequences of EIF6 missense mutations, we cloned 7 patient-derived mutations and generated cell lines expressing wild-type or mutant EIF6 cDNA. We found six mutants (I13N, R67W, G69S, P73R, A194T, G196R) reduced levels of EIF6 protein compared with wild type EIF6, despite comparable abundance of mRNA. The most common recurrent mutation, N106S, was found in 20% of patients and, by contrast to others listed above, did not change protein expression. This mutation is located at the EIF6/60S protein interface and disrupted the interaction of N106S-EIF6 with the 60S subunit as measured by polysome profiling followed by western blotting. To compare the effects of EIF6 versus TP53 somatic mutations in context of SDS deficient translation, we measured ribosome maturation and translation in SDS cells containing shRNAs targeting EIF6 or TP53. EIF6 knockdown ameliorated the SDS defect, reflected by improved ribosome joining (normalization of the 80:60s ratio) and enhanced protein translation (increased O-propargyl-puromycin incorporation), whereas TP53 knockdown had no effect. Knockdown of EIF6 in SDS deficient cells decreased p53 pathway activation as demonstrated by decreased CDKN1A expression. TP53 mutations were significantly associated with MN diagnosis (p=0.023), but were also common in SDS CH and typically stable over time. To identify the characteristics associated with transformation, we analyzed exomes from 7 patients with TP53 mutated myeloid malignancy for allelic imbalances at the TP53 locus and found that all 7 had biallelic alteration of TP53. Using single cell DNA sequencing from serial samples, we observed that TP53 LOH can precede transformation by several years and can distinguish pre-leukemic clones from indolent clones with monoallelic TP53 alterations. Somatic EIF6 mutations were not found in the leukemic clones. These results suggest early detection of TP53 LOH may distinguish clones with leukemic potential. Conclusions: In SDS, impairment of ribosome maturation drives selection of clones with somatic EIF6 or TP53 mutations. EIF6 mutations promote competitive fitness by rescuing the SDS ribosome defect and decreasing p53 pathway activation, and do not contribute to malignant transformation. TP53 mutations decrease checkpoint activation without affecting ribosome assembly. These results provide genetic evidence that germline SBDS deficiency causes a global, disease-specific HSC fitness constraint that drives parallel development of somatic CH and provides a mechanistic rationale for clinical surveillance. Disclosures Dale: Emendo BioTherapeutics: Consultancy; X4 Pharmaceuticals: Research Funding; X4 Pharmaceuticals: Honoraria. Gansner:Alnylam Pharmaceuticals: Current Employment, Current equity holder in private company. Edwards:Jazz Pharmaceuticals: Consultancy, Honoraria. Fleming:DISC Medicine: Consultancy, Membership on an entity's Board of Directors or advisory committees. Lindsley:MedImmune: Research Funding; Takeda Pharmaceuticals: Consultancy; Bluebird Bio: Consultancy; Jazz Pharmaceuticals: Consultancy, Research Funding.

Our report explores the complex role that nuclear factor-kappa B (NF-κB) plays in thrombosis formation, inflammation, and immunity; while additionally demonstrating that patients with NF-κB pathway pathogenic variants appear to carry a substantial thrombotic risk, particularly when secondary thrombotic risk factors are present. We propose that prophylactic anticoagulation should be strongly considered in such patients during high-risk situations and provide additional hematologic management strategies for those with NF-κB pathway alterations. We hope our work also calls to attention the potential need for a broader assessment of venous thromboembolism risk in patients with immune dysregulation to better delineate which patient populations may benefit from anticoagulation prophylaxis.

Both pediatric and adult patients with a primary immunodeficiency/immune dysregulation (PID/PIDR) diagnosis report inferior quality of life (QOL) and patient-reported outcomes (PROs) as compared with their healthy peers. Recognition of the negative impact on QOL and PROs provides an opportunity for clinicians to intervene with supportive measures. However, provider perceptions of PID/PIDR patients’ quality of life, physical well-being, psychosocial health and neurocognition, and access to supportive resources have yet to be systematically evaluated. We report specialty providers’ perception of the QOL and psychosocial and physical well-being of their pediatric and adult patients with PID/PIDR through the utilization of an online survey assessing QOL and the impact of disease or its associated treatment on their physical well-being, mental health, social relationships, neurocognition, and work/school performance. Clinicians trended towards believing adult PID/PIDR patients had worse overall QOL than children with PID/PIDR. Providers additionally identified their adult patients’ QOL to be more deleteriously affected by co-morbidities than their pediatric patients. Clinicians distinguished anxiety and social relationships as the psychosocial aspects most often affected by a complex immunological diagnosis in all patients. Of physical health considerations, energy, rather than mobility or pain, was perceived to be more negatively influenced by PID/PIDR in both adult and pediatric patients. Knowledge of these clinician perceptions can affect communication of findings with patients, as well as ongoing management, and thus, it is important to understand these fully to improve healthcare delivery to, and clinical management of, these patients.

Background:Rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation (ROHHAD) is a rare syndrome with unknown etiology. Metabolic abnormalities are not known to be part of the syndrome. We present one of the oldest cases reported in the literature, who developed severe metabolic abnormalities and hepatic disease suggesting that these features may be part of the syndrome.Case presentation:A 27-year-old woman, diagnosed with ROHHAD syndrome at age 15, who previously developed diabetes insipidus, growth hormone deficiency, hyperprolactinemia, and hypothyroidism in her first decade of life. This was followed by insulin resistance, NAFLD, liver fibrosis, and splenomegaly before age 14 years. Her regimen included a short course of growth hormone, and cyclic estrogen and progesterone. Her metabolic deterioration continued despite treatment with metformin. Interestingly, she had a favorable response to liraglutide therapy despite having a centrally mediated cause for her obesity. At age 26, a 1.6 cm lesion was found incidentally in her liver. Liver biopsy showed hepatocellular carcinoma which was successfully treated with radiofrequency ablation.Conclusion:Metabolic abnormalities, Insulin resistance and fatty liver disease are potentially part of the ROHHAD syndrome that may develop over time. GLP1 agonists were reasonably effective to treat insulin resistance and hyperphagia. Patients with ROHHAD may benefit from close follow up in regards to liver disease.Keywords:Atypical diabetes; GLP-1 agonists; Insulin resistance; Obesity; ROHHAD.

Acquired generalized lipodystrophy (AGL) is a rare disease which develops during early childhood and adolescence, characterized by selective loss of adipose tissue from large regions of the body. Diabetes mellitus with insulin resistance, hepatomegaly, and hypertriglyceridemia develop as a result of the fat loss. In addition to the symptoms associated with fat loss, patients with the autoimmune variety of AGL (Type 2) present with multiple autoimmune diseases. Recently a case of AGL with multiple autoimmune diseases was reported to harbor a mutation in the AIRE gene. Here we report a heterozygous variant (c.4_5insGTTGG, p.Ala2GlyfsTer14) resulting in haploinsufficiency in the immune checkpoint protein CTLA-4, identified in a patient with AGL and accompanying complex autoimmune cluster. The patient was born term with a normal spontaneous vaginal delivery and no complications. At age 6 months, she developed failure to thrive followed by type 1 diabetes and hypertriglyceridemia by ages 2 and 4 years, respectively, and was diagnosed with AGL. Her childhood clinical course was further complicated by poor weight gain despite adequate calorie intake, hepatomegaly with massive splenomegaly and chronic severe diarrhea (onset age 8 years). Her family history is notable for type 1 diabetes in her maternal uncle, type 1 diabetes, recurrent infections, cytopenias, and a mildly hypocellular bone marrow in her maternal cousin, hypothyroidism in her mother and maternal grandfather, and Addison's disease in her maternal grandfather. She presented to Michigan Medicine in acute liver failure and severe jaundice at the age of 14 years. She had mixed inflammatory hepatitis on liver biopsy. With supportive care, her condition improved, but it was noted that she had autoimmune enteropathy and Coombs-positive hemolytic anemia with thrombotic microangiopathy and subsequently developed nephrotic syndrome and progressive kidney insufficiency. Her lipodystrophy related abnormalities included severe insulin resistance (280 units /day with body weight: 41 lbs, hbA1c: 10.7), acanthosis nigricans and severe hypertriglyceridemia (varying between 600 to 6000 mg/dL) and hypertrophic cardiomyopathy. Recombinant metreleptin therapy was utilized during a 9-month hospitalization in 2016, but the patient could not sustain daily injections as an outpatient. Despite aggressive treatment of her kidney disease with specific immune therapies, her kidney disease and her enteropathy progressed. She is currently on hemodialysis, IVIG therapy, and abatacept, vedolizumab, and pentamidine. In conclusion, we report the novel association of CTLA-4 haploinsufficiency and concurrent presence of AGL and providing evidence that AGL can occur within the spectrum of immune dysregulation syndromes, opening the door to investigating these pathways as an etiology for an autoimmune variety of AGL.

Many primary immunodeficiencies (PIDs) manifest in the neonatal period but can be challenging to diagnose and manage optimally. In part, the difficulty stems from the natural immaturity of the neonatal immune system that may mask immune deficits and/or complicate interpretation of clinical findings and laboratory assays. The great diversity of PIDs--from innate immune system defects to those that impact the humoral and/or cellular components of the adaptive immune system--and the rapid rate at which new PIDs are being discovered makes it challenging for practitioners to stay current. Moreover, recent appreciation for immune deficiencies that lead to autoinflammation and autoimmunity have broadened the spectrum of neonatal PID, adding additional complexity to an already intricate field. This article serves to highlight the deficiencies in the neonatal immune system, while providing a review of the more common PIDs that present in the neonate and guidelines for diagnosis and supportive care.

Considerable variation in the management of fever and neutropenia (FN) exists, with factors associated with treatment variation not well described. An on-line survey of 90 pediatric cancer providers in Michigan was performed in Spring 2014. The survey frame was pediatric patients with cancer receiving treatment, with a Port-a-cath, who were clinically stable. Criteria for “Decreased” and “Increased” risk groups were defined by respondents. Survey questions addressed FN definitions, risk groups conceptualization, routine clinical practice, and management guidelines, in the context of risk groups and distance to treating institution. Fifty providers responded (56%), the majority defined a febrile event as temperature >38.3°C and/or two events > 38.0°C within a 24-hour period. Neutropenia was defined as current or anticipated absolute neutrophil count (ANC) 2 hours away. Respondents were significantly more likely to have a “Decreased Risk” patient travel over 2 hours if they rated the local ED as “Poor to Fair” on ability to access Port-a-caths (p 0.048). Most respondents would discharge patients who are afebrile for 24 hours, blood cultures negative for 48 hours, and neutrophil count of greater than 200/μL. 40% preferred discharge on oral antibiotics when the ANC

Immune dysregulation and predisposition to malignancies are critical comorbidities in children affected with ataxia telangiectasia. In addition, these children exhibit increased toxicity to conventional cancer therapy and dose reductions have been proposed to prevent life threatening adverse effects. These modifications to the treatment regimen may result in suboptimal outcomes for these patients. Our report of 3 children with ataxia telangiectasia and cancer highlight the immense challenges in the management of these children, underlining the need for the development of novel, biological agents with reduced acute and long-term side effects in the treatment of cancers in these children.