Genotype-phenotype correlations in chronic granulomatous disease: insights from a large national cohort.

ABSTRACT: Neutrophils are the first line of defense against invading pathogens. Neutrophils execute and modulate immune responses by generating reactive oxygen species (ROS). Chronic granulomatous disease (CGD) is a primary immune deficiency disorder of phagocytes, caused by inherited mutations in the genes of the nicotinamide adenine dinucleotide phosphate reduced oxidase enzyme. These mutations lead to failure of ROS generation followed by recurrent bacterial and fungal infections, frequently associated with hyperinflammatory manifestations. We report a multicenter cumulative experience in diagnosing and treating patients with CGD. From 1986 to 2021, 2918 patients experiencing frequent infections were referred for neutrophil evaluation. Among them, 110 patients were diagnosed with CGD: 56 of Jewish ancestry, 48 of Arabic ancestry, and 6 of non-Jewish/non-Arabic ancestry. As opposed to other Western countries, the autosomal recessive (AR) CGD subtypes were predominant in Israel (71/110 patients). Thirty-nine patients had X-linked CGD, in most patients associated with severe infections (clinical severity score ≥3) and poor outcomes, presenting at a significantly earlier age than AR-CGD subtypes. The full spectrum of infections and hyperinflammatory manifestations is described. Six patients had hypomorphic mutations with significantly milder phenotype, clinical severity score ≤2, and better outcomes. Hematopoietic stem cell transplantation was implemented in 39 of 110 patients (35.5%). Successful engraftment was achieved in 92%, with 82% long-term survival and 71% full clinical recovery. CGD is a complex disorder requiring a multiprofessional team. Early identification of the genetic mutation is essential for prompt diagnosis, suitable management, and prevention.

Successful Haematopoietic Stem Cell Transplantation for LRBA Deficiency with Fludarabine, Treosulfan, and Thiotepa-Based Conditioning.

LRBA deficiency is an inborn error of immunity defined by autoimmunity, lymphoproliferation, recurrent infections, cytopenia, and inflammatory bowel disease. Despite recent advances in managing this disease with targeted biologic therapy, haematopoietic stem cell transplant (HSCT) remains the only cure. However, great variability exists between protocols used to transplant patients with LRBA deficiency. We describe a cohort of seven patients with LRBA deficiency who underwent HSCT using a myeloablative, reduced toxicity regime of fludarabine, treosulfan, and thiotepa at two transplantation centres from 2016 to 2019. Data were collected both retrospectively and prospectively, measuring time to engraftment, infectious complications, incidence of graft versus host disease, and post-transplantation chimerism. Six of seven patients survived transplantation, and four of six surviving patients achieving treatment-free survival. We thus recommend that HSCT with fludarabine, treosulfan, and thiotepa-based conditioning be considered in patients with LRBA deficiency.

Management of Atopy with Dupilumab and Omalizumab in CADINS Disease.

The caspase activation and recruitment domain 11 (CARD11) gene encodes a scaffold protein required for lymphocyte antigen receptor signaling. Dominant-negative, loss-of-function (LOF) pathogenic variants in CARD11 result in CARD11-associated atopy with dominant interference of NF-κB signaling (CADINS) disease. Patients with CADINS suffer with severe atopic manifestations including atopic dermatitis, food allergy, and chronic spontaneous urticaria in addition to recurrent infections and autoimmunity. We assessed the response of dupilumab in five patients and omalizumab in one patient with CADINS for the treatment of severe atopic symptoms. CARD11 mutations were validated for pathogenicity using a T cell transfection assay to assess the impact on activation-induced signaling to NF-κB. Three children and three adults with dominant-negative CARD11 LOF mutations were included. All developed atopic disease in infancy or early childhood. In five patients, atopic dermatitis was severe and recalcitrant to standard topical and systemic medications; one adult suffered from chronic spontaneous urticaria. Subcutaneous dupilumab was initiated to treat atopic dermatitis and omalizumab to treat chronic spontaneous urticaria. All six patients had rapid and sustained improvement in atopic symptoms with no complications during the follow-up period. Previous medications used to treat atopy were able to be decreased or discontinued. In conclusion, treatment with dupilumab and omalizumab for severe, refractory atopic disease in patients with CADINS appears to be effective and well tolerated in patients with CADINS with severe atopy.

Biallelic Loss of Function Variants in SENP7 Cause Immunodeficiency with Neurologic and Muscular Phenotypes.

To evaluate a novel candidate disease gene, we engaged international collaborators and identified rare, biallelic, specifically homozygous, loss of function variants in SENP7 in 4 children from 3 unrelated families presenting with neurodevelopmental abnormalities, dysmorphism, and immunodeficiency. Their clinical presentations were characterized by hypogammaglobulinemia, intermittent neutropenia, and ultimately death in infancy for all 4 patients. SENP7 is a sentrin-specific protease involved in posttranslational modification of proteins essential for cell regulation, via a process referred to as deSUMOylation. We propose that deficiency of deSUMOylation may represent a novel mechanism of primary immunodeficiency.

Two decades of stem cell transplantation in patients with Fanconi anemia: Analysis of factors affecting transplant outcomes.

Allogeneic hematopoietic stem cell transplantation (HSCT) is currently the only curative treatment for the hematological complications of patients with Fanconi anemia (FA). Over the last two decades, HSCT outcomes have improved dramatically following the development of regimens tailored for FA patients. In this study, we analyzed genetic, clinical, and transplant data of 41 patients with FA who underwent HSCT at Hadassah Medical Center between November 1996 and September 2020. Overall survival (OS) was 82.9% with a median follow-up time of 2.11-years (95% CI, .48-16.56). Thirteen patients (31.7%) developed acute graft-versus-host disease (GVHD), three of them with grades 3-4. Nine patients developed chronic GVHD, five had extensive disease. Twelve patients (29.3%) developed stable mixed-chimerism with complete resolution of bone marrow failure (BMF); none of them had acute nor chronic GVHD. Significantly higher GVHD rates were observed in transplants from peripheral blood stem cell grafts as compared to other stem cell sources (p = .002 for acute and p = .004 for chronic GVHD). Outcome parameters were comparable between HSCT from matched-sibling (n = 20) to other donors (n = 21), including survival rates (p = .1), time to engraftment (p = .69 and p = .14 for neutrophil and platelet engraftment time, respectively), chimerism status (p = .36 and p = .83 for full-donor and mixed chimerism, respectively), and GVHD prevalence (p = 1). Our results demonstrate the vast improvements in HSCT outcomes of patients with FA, narrowing the gap between matched-sibling versus alternative donor transplantations. Our data identifies factors that may significantly affect transplant outcomes such as graft source and chimerism status.

Vedolizumab for pediatric patients with gastrointestinal acute graft-versus-host-disease.

Vedolizumab, an anti-α4ß7 integrin monoclonal antibody, impairs homing of T-cells to the gastrointestinal (GI) endothelium and acts as a gut-selective anti-inflammatory agent. Recent reports of the efficacy of vedolizumab in treating lower GI acute graft-versus-host disease (aGVHD) are promising, but experience in children is scarce. We present a cohort of 13 pediatric patients who were treated with vedolizumab for GI aGVHD. Ten of the patients were treated for steroid-refractory disease, out of which, six suffered from severe (stage 3 or 4) GI disease before the first dose of vedolizumab. In the other three patients, vedolizumab was introduced early in the disease course. Median time between GI GVHD onset to vedolizumab treatment was 23 days (range 7-59 days), with a median of 3 doses (range 1-5) per patient. GI GVHD staging was evaluated at various time points after the first vedolizumab dose, showing improvement in nine of the 13 patients. After a median follow-up time of 13 months (range 6-34 months), eight patients completely recovered, two had ongoing chronic colitis, and three patients died. During the vedolizumab treatment period, 38 infectious episodes were noted, most of them GI related. The unique activity profile of vedolizumab makes it an appealing treatment option for lower GI aGVHD, but caution for concurrent infections is warranted.

Social determinants of health and primary immunodeficiency.

OBJECTIVE: Inborn errors of immunity (IEI) are rare genetic conditions affecting the immune system. The rate of IEI and their presentation, course, and treatment are all affected by a multitude of social determinants, eventually affecting prognosis. This review summarizes the current knowledge of the social determinants affecting infectious susceptibility, genetic predisposition, diagnosis, and treatment of IEI. DATA SOURCES: PubMed. STUDY SELECTIONS: Search terms included "consanguinity," "social determinants," and "founder effect." Further studies were selected based on relevant citations. RESULTS: Changes in climate and human behavior have modulated the spread of disease vectors and infectious organisms. Consanguinity increases the rate of autosomal recessive conditions, changes the distribution, and affects the severity of IEI. Access to sophisticated genetic and immunologic diagnostic modalities affects genetic counseling and timely diagnosis. Effective genetic counseling should address to the patient's genetic background and ethical code. Access to appropriate and timely treatment of immunodeficiencies is scarce in some regions of the world. CONCLUSION: High consanguinity rate and reduced access to prophylactic measures increase the burden of immunodeficiencies in many low- and medium-income countries. Furthermore, poor access to diagnostic and treatment modalities in these regions adversely affects patients' prognosis. Increased awareness among health care professionals and the public and increased collaboration with Western countries aid in diagnosis of these conditions. Further advancements require improved public funding to the prevention, diagnosis, and treatment of IEI.

Bacillus Calmette-Guerin (BCG) Vaccine-associated Complications in Immunodeficient Patients Following Stem Cell Transplantation.

PURPOSE: Bacillus Calmette-Guerin (BCG) is a live attenuated vaccine with the potential of causing severe iatrogenic complications in patients with primary immunodeficiency diseases (PID) before and after hematopoietic stem cell transplantation (HSCT). We aim to investigate risk factors of post-HSCT BCG-related complications in PID patients. METHODS: A retrospective analysis of pediatric PID patients who had received the BCG vaccine and underwent HSCT at Hadassah-Hebrew University Medical Center, between 2007 and 2019. RESULTS: We found 15/36 (41.67%) patients who developed post-HSCT BCG-related complications. The most significant risk factor for developing BCG-related complications was T cell deficiency (47.6% of the non-complicated vs 83.3% of the BCGitis and 100% of the BCGosis groups had T cell lymphopenia, p = 0.013). None of the chronic granulomatous patients developed BCG-related manifestation post-transplant. Among T cell-deficient patients, lower NK (127 vs 698 cells/µl, p = 0.04) cell counts and NK-SCID were risk factors for ongoing post-HSCT BCGosis, as was pretransplant disseminated BCGosis (33.3% of patients with BCGosis vs none of the non-BCGosis patients, p = 0.04). Immune reconstitution inflammatory syndrome (IRIS) was observed in 3/5 patients with Omenn syndrome. Prophylactic antimycobacterial treatment was not proven effective. CONCLUSION: BCG vaccination can cause significant morbidity and mortality in the post-transplant T cell-deficient patient, especially in the presence of pre-transplant disease. Taking a detailed medical history prior to administering, the BCG vaccine is crucial for prevention of this complication.

Characterization of the clinical and immunologic phenotype and management of 157 individuals with 56 distinct heterozygous NFKB1 mutations.

BACKGROUND: An increasing number of NFKB1 variants are being identified in patients with heterogeneous immunologic phenotypes. OBJECTIVE: To characterize the clinical and cellular phenotype as well as the management of patients with heterozygous NFKB1 mutations. METHODS: In a worldwide collaborative effort, we evaluated 231 individuals harboring 105 distinct heterozygous NFKB1 variants. To provide evidence for pathogenicity, each variant was assessed in silico; in addition, 32 variants were assessed by functional in vitro testing of nuclear factor of kappa light polypeptide gene enhancer in B cells (NF-κB) signaling. RESULTS: We classified 56 of the 105 distinct NFKB1 variants in 157 individuals from 68 unrelated families as pathogenic. Incomplete clinical penetrance (70%) and age-dependent severity of NFKB1-related phenotypes were observed. The phenotype included hypogammaglobulinemia (88.9%), reduced switched memory B cells (60.3%), and respiratory (83%) and gastrointestinal (28.6%) infections, thus characterizing the disorder as primary immunodeficiency. However, the high frequency of autoimmunity (57.4%), lymphoproliferation (52.4%), noninfectious enteropathy (23.1%), opportunistic infections (15.7%), autoinflammation (29.6%), and malignancy (16.8%) identified NF-κB1-related disease as an inborn error of immunity with immune dysregulation, rather than a mere primary immunodeficiency. Current treatment includes immunoglobulin replacement and immunosuppressive agents. CONCLUSIONS: We present a comprehensive clinical overview of the NF-κB1-related phenotype, which includes immunodeficiency, autoimmunity, autoinflammation, and cancer. Because of its multisystem involvement, clinicians from each and every medical discipline need to be made aware of this autosomal-dominant disease. Hematopoietic stem cell transplantation and NF-κB1 pathway-targeted therapeutic strategies should be considered in the future.

The Broad Clinical Spectrum and Transplant Results of PNP Deficiency.

PURPOSE: Purine nucleoside phosphorylase (PNP) is a known yet rare cause of combined immunodeficiency with a heterogeneous clinical presentation. We aim to add to the expanding clinical spectrum of disease, and to summarize the available data on bone marrow transplant for this condition. METHODS: Data was collected from patient files retrospectively. A review of the literature of hematopoietic stem cell transplantation (HSCT) for PNP deficiency was conducted. RESULTS: Four patients were treated in two centers in Israel. One patient died of EBV-related lymphoma with CNS involvement prior to transplant. The other three patients underwent successful HSCT with good immune reconstitution post-transplant (follow-up 8-108 months) and excellent neurological outcomes. CONCLUSION: PNP is a variable immunodeficiency and should be considered in various clinical contexts, with or without neurological manifestations. HSCT offers a good treatment option, with excellent clinical outcomes, when preformed in a timely manner.

Successful treatment with daratumumab for post-HSCT refractory hemolytic anemia.

Autoimmune cytopenias (AIC) following allogeneic hematopoietic stem cell transplantation (HSCT) may cause significant morbidity and mortality and are often challenging to treat. We present a case of a pediatric patient with primary myelofibrosis of infancy caused by VPS45 protein deficiency, who developed severe refractory hemolytic anemia and immune-mediated thrombocytopenia 3.5 months following HSCT. After the failure of several treatments, he received daratumumab, an anti-CD38 specific antibody, and demonstrated fast and sustained response. The only side effect was delayed recovery of humoral immunity. Daratumumab, by targeting antibody-producing plasma cells, may be a valid treatment option for refractory post-HSCT AIC.

Combined immunodeficiency and atopy caused by a dominant negative mutation in caspase activation and recruitment domain family member 11 (CARD11).

BACKGROUND: Combined immunodeficiency (CID) is a T-cell defect frequently presenting with recurrent infections, as well as associated immune dysregulation manifesting as autoimmunity or allergic inflammation. OBJECTIVE: We sought to identify the genetic aberration in 4 related patients with CID, early-onset asthma, eczema, and food allergies, as well as autoimmunity. METHODS: We performed whole-exome sequencing, followed by Sanger confirmation, assessment of the genetic variant effect on cell signaling, and evaluation of the resultant immune function. RESULTS: A heterozygous novel c.C88T 1-bp substitution resulting in amino acid change R30W in caspase activation and recruitment domain family member 11 (CARD11) was identified by using whole-exome sequencing and segregated perfectly to family members with severe atopy only but was not found in healthy subjects. We demonstrate that the R30W mutation results in loss of function while also exerting a dominant negative effect on wild-type CARD11. The CARD11 defect altered the classical nuclear factor κB pathway, resulting in poor in vitro T-cell responses to mitogens and antigens caused by reduced secretion of IFN-γ and IL-2. CONCLUSION: Unlike patients with biallelic mutations in CARD11 causing severe CID, the R30W defect results in a less profound yet prominent susceptibility to infections, as well as multiorgan atopy and autoimmunity.

Bone marrow transplantation for non-malignant diseases using treosulfan-based conditioning.

BACKGROUND: Treosulfan (treo) is an alkylating agent with a low acute toxicity profile that is increasingly used in hematopoietic stem cell transplantation, predominantly in non-malignant diseases. Treosulfan is usually combined with additional agents, but there is scant evidence to allow comparison between different conditioning protocols using treosulfan. We present the experience of three pediatric transplantation centers in Israel using different treosulfan-based conditioning regimens. PROCEDURE: Data were collected retrospectively on 44 children who underwent 45 hematopoietic stem cell transplantations using treosulfan in combination with either fludarabine (flu) and thiotepa (tt) (n = 20), cyclophosphamide (cy) (n = 6) or fludarabine alone (n = 19). RESULTS: Overall survival (OS) was 70.5%. Disease free survival (DFS) was 54.6%. There was no statistically significant difference between treatment groups in either OS or DFS. Overall survival in patients younger than one year was higher (88.2%). There were significantly more patients with 100% donor chimerism transplanted with flu/treo/tt compared with flu/treo or treo/cy (94.7% compared to 66.7% and 16.7%, respectively). Further prospective studies are required to determine the optimal treosulfan-based preparative regimen for children with non-malignant diseases. Pediatr Blood Cancer 2015;62:299-304. © 2014 Wiley Periodicals, Inc.

Risk and promise: an 11-year, single-center retrospective study of severe acute GVHD in pediatric patients undergoing allogeneic HSCT for nonmalignant diseases.

Background: Hematopoietic stem cell transplantation (HSCT) is the only curative option for many nonmalignant hematopoietic-derived diseases in pediatric patients. Survival after HSCT has improved in recent years and resulted in a 90% survival rate and cure in some nonmalignant diseases. Graft-vs.-host disease (GVHD) remains a frequent and major complication of HSCT, and a leading cause of morbidity and mortality. Prognosis of patients with high-grade GVHD is dismal, with survival rates varying from 25% in the adult population to 55% in pediatric patients. Methods: The main aim of this study is to evaluate the incidence, risk factors, and outcome of severe acute GVHD (AGVHD) in pediatric patients with nonmalignant diseases, following allogeneic HSCT. Clinical and transplant data were retrospectively collected for all pediatric patients who underwent allogeneic HSCT for nonmalignant diseases at the Hadassah Medical Center between 2008 and 2019. Patients who developed severe AGVHD were compared with those who did not. Results: A total of 247 children with nonmalignant diseases underwent 266 allogeneic HSCTs at Hadassah University Hospital over an 11-year period. Seventy-two patients (29.1%) developed AGVHD, 35 of them (14.1%) severe AGVHD (grade 3-4). Significant risk factors for developing severe AGVHD were unrelated donor (p < 0.001), mismatch donor (p < 0.001), and the use of peripheral blood stem cells (PBSCs) (p < 0.001). Survival rates of pediatric patients with severe AGVHD was 71.4%, compared with 91.9% among those with mild (grade 1-2) AGVHD and 83.4% among patients without AGVHD (p = 0.067). Conclusions: These results demonstrate a high survival rate in pediatric patients with nonmalignant diseases despite severe GVHD. Significant mortality risk factors found in these patients were the source of donor PBSC (p = 0.016) and poor response to steroid treatment (p = 0.007).

Human CARMIL2 deficiency underlies a broader immunological and clinical phenotype than CD28 deficiency.

Patients with inherited CARMIL2 or CD28 deficiency have defective T cell CD28 signaling, but their immunological and clinical phenotypes remain largely unknown. We show that only one of three CARMIL2 isoforms is produced and functional across leukocyte subsets. Tested mutant CARMIL2 alleles from 89 patients and 52 families impair canonical NF-κB but not AP-1 and NFAT activation in T cells stimulated via CD28. Like CD28-deficient patients, CARMIL2-deficient patients display recalcitrant warts and low blood counts of CD4+ and CD8+ memory T cells and CD4+ TREGs. Unlike CD28-deficient patients, they have low counts of NK cells and memory B cells, and their antibody responses are weak. CARMIL2 deficiency is fully penetrant by the age of 10 yr and is characterized by numerous infections, EBV+ smooth muscle tumors, and mucocutaneous inflammation, including inflammatory bowel disease. Patients with somatic reversions of a mutant allele in CD4+ T cells have milder phenotypes. Our study suggests that CARMIL2 governs immunological pathways beyond CD28.

Autoimmune Cytopenias Post Hematopoietic Stem Cell Transplantation in Pediatric Patients With Osteopetrosis and Other Nonmalignant Diseases.

Autoimmune cytopenia (AIC) is a rare complication post hematopoietic stem cell transplantation (HSCT), with a higher incidence in nonmalignant diseases. The etiology of post-HSCT AIC is poorly understood, and in many cases, the cytopenia is prolonged and refractory to treatment. Diagnosis of post-HSCT AIC may be challenging, and there is no consensus for a standard of care. In this retrospective study, we summarize our experience over the past five years with post-HSCT AIC in pediatric patients with osteopetrosis and other nonmalignant diseases. All pediatric patients who underwent HSCT for nonmalignant diseases at Hadassah Medical Center over the past five years were screened for post-HSCT AIC, and data were collected from the patient's medical records. From January 2017 through December 2021, 140 pediatric patients underwent HSCT for osteopetrosis (n=40), and a variety of other nonmalignant diseases. Thirteen patients (9.3%) presented with post-HSCT AIC. Of these, 7 had osteopetrosis (17.5%), and 6 had other underlying nonmalignant diseases. Factors associated with developing AIC included unrelated or non-sibling family donors (n=10), mixed chimerism (n=6), and chronic GvHD (n=5). Treatment modalities included steroids, IVIG, rituximab, bortezomib, daratumumab, eltrombopag, plasmapheresis, and repeated HSCT. Response to treatment was variable; Seven patients (54%) recovered completely, and three patients (23%) recovered partially, still suffering from mild-moderate thrombocytopenia. Three patients died (23%), two following progressive lung disease and one from sepsis and multi-organ failure after a 3rd HSCT. In our experience, post-HSCT AICs in pediatric patients with nonmalignant diseases may pose a challenging post-transplant complication with a variable presentation and a wide spectrum of severity. A relatively high prevalence is seen in patients with osteopetrosis, possibly due to difficult engraftment and high rates of mixed chimerism. There is a dire need for novel treatment modalities for better management of the more severe and refractory cases.

Neurological complications following pediatric allogeneic hematopoietic stem cell transplantation: Risk factors and outcome.

Background: Allogeneic hematopoietic stem cell transplantation (HSCT) is an efficient treatment for numerous malignant and nonmalignant conditions affecting children. This procedure can result in infectious and noninfectious neurological complications (NCs). Objective: The objective of the study is to examine the incidence, risk factors, and outcomes of NCs in pediatric patients following allogeneic HSCT. Methods: We performed a retrospective study of 746 children who underwent 943 allogeneic HSCTs in two large pediatric hospitals in Israel from January 2000 to December 2019. Results: Of the pediatric patients 107 (14.3%) experienced 150 NCs. The median follow-up was 55 months. Noninfectious NCs were more common than infectious NCs (81.3% vs. 18.7%). Factors significantly associated with type of NC (infectious vs. noninfectious) were underlying disease (immunodeficiency vs. malignant and metabolic/hematologic disease) (p-value = 0.000), and use of immunosuppressive agent, either Campath or ATG (p-value = 0.041). Factors with a significant impact on developing neurological sequelae post-NC were number of HSCT >1 (p-value = 0.028), the use of alemtuzumab as an immunosuppressive agent (p-value = 0.003), and infectious type of NC (p-value = 0.046). The overall survival rate of whole NC-cohort was 44%; one-third of all mortality cases were attributed to the NC. The strongest prognostic factors associated with mortality were older age at HSCT (p-value = 0.000), the use of alemtuzumab as an immunosuppressive agent (p-value = 0.004), and the existence of neurological sequelae (p-value = 0.000). Abnormal central nervous system imaging (p-value = 0.013), the use of alemtuzumab as an immunosuppressive agent (p-value = 0.019), and neurological sequelae (p-value = 0.000) had statistically significant effects on neurological cause of death. Conclusion: Infectious and noninfectious NCs are a significant cause of morbidity and mortality following allogeneic HSCT in children. Further research is required to better understand the risk factors for different NCs and their outcomes regarding sequelae and survival.

Haploidentical stem cell transplantation with post-transplant cyclophosphamide for osteopetrosis and other nonmalignant diseases.

Allogeneic hematopoietic stem cell transplantation (HSCT) is curative for a variety of nonmalignant disorders including osteopetrosis, bone marrow failures, and immune deficiencies. Haploidentical HSCT is a readily available option in the absence of a matched donor, but engraftment failure and other post-transplant complications are a concern. Post-transplant cyclophosphamide (PT-Cy) regimens are gaining popularity and recent reports show promising results. We report our experience with nine pediatric patients with nonmalignant diseases who were transplanted from a haploidentical donor with PT-Cy. From 2015 to 2019, nine children with nonmalignant diseases underwent haploidentical HSCT with PT-Cy, two as a second transplant and seven as primary grafts after upfront serotherapy and busulfan-based myeloablative conditioning. Patient's diseases included osteopetrosis (n = 5), congenital amegakaryocytic thrombocytopenia (n = 2), hemophagocytic lymphohistiocytosis (n = 1), and Wiskott Aldrich syndrome (n = 1). Two patients failed to engraft following upfront PT-Cy transplants, one was salvaged with a second PT-Cy transplant, and the other with a CD34+ selected graft. None of the patients suffered from graft-versus-host disease. Three patients died from early posttransplant infectious complications and six patients are alive and well. In conclusion, haploidentical HSCT with PT-Cy is a feasible option for pediatric patients with nonmalignant diseases lacking a matched donor.

A human case of GIMAP6 deficiency: a novel primary immune deficiency.

The GTPase of immunity-associated proteins (GIMAPs) are a family of genes believed to contribute to lymphocyte development, signaling, and apoptosis, thus playing an important role in immune system homeostasis. While models of gene derangement have been described in both mice and immortalized cell lines, human examples of these diseases remain exceptionally rare. In this manuscript we describe the first documented human cases of a homozygous deleterious GIMAP6 variant in the GIMAP6 gene and their subsequent clinical and immunological phenotype. In order to interrogate the patients' immune defect, we performed whole-exome sequencing, western blot, flow cytometry analysis, lymphocyte activation and proliferation studies, cytokine release assays, and apoptosis studies. We found two siblings with a predicted deleterious homozygous variant in the GIMAP6 gene with no expression of GIMAP6 protein on western blot. Patients demonstrated accelerated apoptosis, but largely normal lymphocyte subpopulations, activation and proliferation and cytokine release. There appears to be a spectrum of clinical features associated with deficiency of GIMAP6 protein, with one patient suffering lymphopenia and recurrent sinopulmonary infections, and the other clinically asymptomatic. Biallelic variants in the GIMAP6 gene have now been shown to demonstrate disease in humans. The absence of GIMAP6 protein is associated with a spectrum of clinical manifestations and much remains to be learnt about the pathogenic mechanisms underlying this disease. We suggest that biallelic variants in the gene for GIMAP6 should be considered in children with lymphopenia and recurrent sinopulmonary infections.