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Single allele mutations in the Cell Division Control protein 42 homolog (CDC42) gene were recently shown to cause Takenouchi-Kosaki syndrome with diverse manifestations. These include persistent mild thrombocytopenia with large platelet size, severe developmental delay, growth retardation, facial dysmorphism, and other neurodevelopmental and hematological anomalies. CDC42 deficiency might also cause myelofibrosis, myeloproliferation, and severe autoinflammation. CDC42 closely interacts with the Wiskott-Aldrich Syndrome Protein, but little is still known about the immune abnormalities associated with CDC42 deficiency. Detailed immune evaluations were performed in a patient diagnosed with a CDC42 Tyr64Cys mutation. The 19-year-old female suffered from recurrent pneumonia, otitis media, and bacteremia, which resolved at 10 years of age, concordant with the initiation of amoxicillin prophylaxis. In addition, the patient had frequent viral upper respiratory tract infections, which resolved without need for medical interventions. Immune evaluations demonstrated decreased immunoglobulin levels, inability to maintain antibody responses, progressive decline in the number of CD19+ B cells, and decreased switched memory B cells. There was also a decrease in CD4+ and CD8+ T cells, markedly reduced naïve T cells, and intermittent depressed proliferation of T cells to stimulation. Natural killer cells' number and functions were normal. However, no opportunistic infections were observed, nor was there evidence for autoinflammation. CDC42 deficiency might also be associated with decline in T and B cell function. Therefore, immunity in patients with CDC42 defects should be closely monitored, particularly among those with frequent infections or systemic autoinflammation.

Introduction: Chronic granulomatous disease (CGD) is an inherited primary immunodeficiency caused by mutations in the NADPH complex characterized by recurrent infections, inflammation and autoimmunity. While autosomal recessive forms exist, X-linked CGD makes up the majority of cases, which is caused by mutations in the CYBB gene. Patients are at high risk for infections with catalase positive bacteria and fungi. The prognosis has improved significantly with improvements in disease detection and management, including prophylactic antibiotic and antifungal therapy. Hematopoietic stem cell transplantation (HSCT) is a curative option for patients with a suitable donor. Aim: To report the clinical presentation, immune features and genetic mutations in 2 patients with novel mutations in the CYBB gene causing X-linked CGD who underwent HSCT. Results: Case 1: Patient 1 is a 14-year-old patient who initially presented with disseminated aspergillosis at the age of 3. He was noted to have an abnormal neutrophil oxidative burst index (NOBI) and genetic testing revealed a mutation in the CYBB gene (c.883_87dupGTGGT) consistent with CGD. He successfully underwent HSCT at age 4. At age 10 he developed a primary intracranial rhabdomyosarcoma in the posterior cranial fossa. Case 2: Patient 2 is a 4-year-old male who was worked up for CGD after developing a perianal abscess at 1 month of age followed by Moraxella bacteremia at 2 months of age. He had 2 abnormal NOBIs and genetic testing identified a novel mutation in the CYBB gene that was thought to explain his phenotype (c.941delA). He underwent an HSCT (10/10 HLA matched unrelated donor). Both patients have had normalization of their NOBI post-transplant and remain free of significant infections. Discussion: We report the clinical presentation, immune features and genetic mutations in 2 patients with novel mutations in the CYBB gene causing X-linked CGD. Identifying pathogenic mutations causing CGD is important for a better understanding of genotype–phenotype associations and disease course in this patient population. Statement of novelty: We describe 2 pediatric patients diagnosed with X-linked chronic granulomatous disease due to novel mutations in the CYBB gene.

Inherited defects that abrogate the function of the adenosine deaminase (ADA) enzyme and consequently lead to the accumulation of toxic purine metabolites cause profound lymphopenia and severe combined immune deficiency. Additionally, neutropenia and impaired neutrophil function have been reported among ADA-deficient patients. However, due to the rarity of the disorder, the neutrophil developmental abnormalities and the mechanisms contributing to them have not been characterized. Induced pluripotent stem cells (iPSC) generated from two unrelated ADA-deficient patients and from healthy controls were differentiated through embryoid bodies into neutrophils. ADA deficiency led to a significant reduction in the number of all early multipotent hematopoietic progenitors. At later stages of differentiation, ADA deficiency impeded the formation of granulocyte colonies in methylcellulose cultures, leading to a significant decrease in the number of neutrophils generated from ADA-deficient iPSCs. The viability and apoptosis of ADA-deficient neutrophils isolated from methylcellulose cultures were unaffected, suggesting that the abnormal purine homeostasis in this condition interferes with differentiation or proliferation. Additionally, there was a significant increase in the percentage of hyperlobular ADA-deficient neutrophils, and these neutrophils demonstrated significantly reduced ability to phagocytize fluorescent microspheres. Supplementing iPSCs and methylcellulose cultures with exogenous ADA, which can correct adenosine metabolism, reversed all abnormalities, cementing the critical role of ADA in neutrophil development. Moreover, chemical inhibition of the ribonucleotide reductase (RNR) enzyme, using hydroxyurea or a combination of nicotinamide and trichostatin A in iPSCs from healthy controls, led to abnormal neutrophil differentiation similar to that observed in ADA deficiency, implicating RNR inhibition as a potential mechanism for the neutrophil abnormalities. In conclusion, the findings presented here demonstrate the important role of ADA in the development and function of neutrophils while clarifying the mechanisms responsible for the neutrophil abnormalities in ADA-deficient patients.

Summary The absence of adenosine deaminase (ADA) causes severe combined immune deficiency (SCID), which has been treated with PEGylated bovine-extracted ADA (ADAGEN). ADAGEN was recently replaced by a PEGylated recombinant bovine ADA, expressed in Escherichia coli (elapegademase, ELA–ADA). Limited information on ELA–ADA is available. ADA enzymatic activity of ELA–ADA and ADAGEN was assessed in vitro at diverse dilutions. ADA activity and immune reconstitution in an ADA–SCID patient treated with ELA–ADA were compared with age-matched patients previously treated with ADAGEN. ADA activity and thymus reconstitution were evaluated in ADA-deficient mice following ELA–ADA or ADAGEN administered from 7 days postpartum. In vitro, ADA activity of ELA–ADA and ADAGEN were similar at all dilutions. In an ADA–SCID patient, ELA–ADA treatment led to a marked increase in trough plasma ADA activity, which was 20% higher than in a patient previously treated with ADAGEN. A marked increase in T cell numbers and generation of naive T cells was evident following 3 months of ELA–ADA treatment, while T cell numbers increased following 4 months in 3 patients previously treated with ADAGEN. T cell proliferations stimulation normalized and thymus shadow became evident following ELA–ADA treatment. ADA activity was significantly increased in the blood of ADA-deficient mice following ELA–ADA compared to ADAGEN, while both treatments improved the mice weights, the weight, number of cells in their thymus and thymocyte subpopulations. ELA–ADA has similar in- vitro and possibly better in-vivo activity than ADAGEN. Future studies will determine whether ELA–ADA results in improved long-term immune reconstitution.

Inherited defects in adenosine deaminase (ADA) cause a subtype of severe combined immunodeficiency (SCID) known as severe combined immune deficiency caused by adenosine deaminase defects (ADA-SCID). Most affected infants can receive a diagnosis while still asymptomatic by using an SCID newborn screening test, allowing early initiation of therapy. We review the evidence currently available and propose a consensus management strategy. In addition to treatment of the immune deficiency seen in patients with ADA-SCID, patients should be followed for specific noninfectious respiratory, neurological, and biochemical complications associated with ADA deficiency. All patients should initially receive enzyme replacement therapy (ERT), followed by definitive treatment with either of 2 equal first-line options. If an HLA-matched sibling donor or HLA-matched family donor is available, allogeneic hematopoietic stem cell transplantation (HSCT) should be pursued. The excellent safety and efficacy observed in more than 100 patients with ADA-SCID who received gammaretrovirus- or lentivirus-mediated autologous hematopoietic stem cell gene therapy (HSC-GT) since 2000 now positions HSC-GT as an equal alternative. If HLA-matched sibling donor/HLA-matched family donor HSCT or HSC-GT are not available or have failed, ERT can be continued or reinstituted, and HSCT with alternative donors should be considered. The outcomes of novel HSCT, ERT, and HSC-GT strategies should be evaluated prospectively in "real-life" conditions to further inform these management guidelines.

Background: Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder that often involves impaired cognition, communication difficulties and restrictive, repetitive behaviors. ASD is extremely heterogeneous both clinically and etiologically, which represents one of the greatest challenges in studying the molecular underpinnings of ASD. While hundreds of ASD-associated genes have been identified that confer varying degrees of risk, no single gene variant accounts for >1% of ASD cases. Notably, a large number of ASD-risk genes function as epigenetic regulators, indicating potential epigenetic dysregulation in ASD. As such, we compared genome-wide DNA methylation (DNAm) in the blood of children with ASD (n = 265) to samples from age- and sex-matched, neurotypical controls (n = 122) using the Illumina Infinium HumanMethylation450 arrays.Results: While DNAm patterns did not distinctly separate ASD cases from controls, our analysis identified an epigenetically unique subset of ASD cases (n = 32); these individuals exhibited significant differential methylation from both controls than the remaining ASD cases. The CpG sites at which this subset was differentially methylated mapped to known ASD risk genes that encode proteins of the nervous and immune systems. Moreover, the observed DNAm differences were attributable to altered blood cell composition, i.e., lower granulocyte proportion and granulocyte-to-lymphocyte ratio in the ASD subset, as compared to the remaining ASD cases and controls. This ASD subset did not differ from the rest of the ASD cases in the frequency or type of high-risk genomic variants.Conclusion: Within our ASD cohort, we identified a subset of individuals that exhibit differential methylation from both controls and the remaining ASD group tightly associated with shifts in immune cell type proportions. This is an important feature that should be assessed in all epigenetic studies of blood cells in ASD. This finding also builds on past reports of changes in the immune systems of children with ASD, supporting the potential role of altered immunological mechanisms in the complex pathophysiology of ASD. The discovery of significant molecular and immunological features in subgroups of individuals with ASD may allow clinicians to better stratify patients, facilitating personalized interventions and improved outcomes.

Introduction: Complete or near complete absence of the purine nucleoside phosphorylase (PNP) enzyme causes a profound T cell immunodeficiency and neurological abnormalities that are often lethal in infancy and early childhood. We hypothesized that patients with partial PNP deficiency, characterized by a late and mild phenotype due to residual PNP enzyme, would provide important information about the minimal PNP activity needed for normal development.Methods: Three siblings with a homozygous PNP gene mutation (c.769C>G, p.His257Asp) resulting in partial PNP deficiency were investigated. PNP activity was semi-quantitively assayed by the conversion of [14C]inosine in hemolysates, mononuclear cells, and lymphoblastoid B cells. PNP protein expression was determined by Western Blotting in lymphoblastoid B cells. DNA repair was quantified by measuring viability of lymphoblastoid B cells following ionizing irradiation.Results: A 21-year-old female was referred for recurrent sino-pulmonary infections while her older male siblings, aged 25- and 28- years, did not suffer from significant infections. Two of the siblings had moderately reduced numbers of T, B, and NK cells, while the other had near normal lymphocyte subset numbers. T cell proliferations were normal in the two siblings tested. Hypogammaglobulinemia was noted in two siblings, including one that required immunoglobulin replacement. All siblings had typical (normal) neurological development. PNP activity in various cells from two patients were 8–11% of the normal level. All siblings had normal blood uric acid and increased PNP substrates in the urine. PNP protein expression in cells from the two patients examined was similar to that observed in cells from healthy controls. The survival of lymphoblastoid B cells from 2 partial PNP-deficient patients after irradiation was similar to that of PNP-proficient cells and markedly higher than the survival of cells from a patient with absent PNP activity or a patient with ataxia telangiectasia.Conclusions: Patients with partial PNP deficiency can present in the third decade of life with mild-moderate immune abnormalities and typical development. Near-normal immunity might be achieved with relatively low PNP activity.

De novo PTAID may develop in pediatric solid organ transplant recipients, have a diverse spectrum, and are occasionally treatment resistant. Previous reports showed resolution of immune cytopenias in solid organ transplant recipients following replacement of the calcineurin inhibitor tacrolimus with the mTOR inhibitor sirolimus. Herein we describe a retrospective review (2000-2017) of subjects who developed PTAID in whom immunosuppression was changed to sirolimus. Eight recipients (6 males) of either liver (n = 7) or multivisceral transplant (n = 1) suffered from severe, treatment-resistant PTAID and were switched from tacrolimus to sirolimus. The median age at transplant was 1 year (range 0.5-2.4 years). Six (75%) recipients developed de novo allergy and 2 immune-mediated diseases. The median age at presentation of PTAID was 2.7 (1.4-9) years at a median of 1.3 (0.25-8) years after transplantation. The median time from PTAID presentation to conversion to sirolimus was 1.8 (0.45-10) years. Complete resolution of symptoms was seen in 4 (50%) patients after a median of 12 (range 4-24) months including 2 patients with immune-mediated disease, 1 eczema, and 1 with eosinophilic colitis. One patient with multiple food allergies had a partial response and 3 (38%) had no response. None of the 8 recipients developed sirolimus-attributed adverse events or acute rejection during a median follow-up of 5 (0.6-8) years after the conversion. Immunosuppression conversion from tacrolimus to sirolimus can be an effective therapy in patients suffering severe or treatment-resistant PTAID, suggesting a potential role for tacrolimus in the pathogenesis of PTAID.

In recent years, the cross talk between the liver and the immune system is being uncovered, in part by studying liver involvement in primary immune deficiencies (PID) and in part by investigating the alterations of the immune system following orthotopic liver transplantation (OLT). Here we review some of the reciprocal interactions between the liver and the immune system. Patients with PID, particularly those involving inherited defects in T and B cells or innate immunity are prone to infections and inflammatory responses that often involve the liver. Omenn's syndrome, familial hemophagocytic lymphohistiocytosis, AIRE, FOXP3 and CD25 deficiencies, common variable immunodeficiency, CD40 ligand deficiency, chronic granulomatous disease and autoimmune lymphoproliferative syndrome are some of the notable PID associated with typical hepatobiliary abnormalities. Knowledge gained from studying these PID together with laboratory and histological evaluations can assist in managing PID-associated liver dysfunction. The liver itself also has important effects on the immune system, as evident from the growing experience with patients surviving OLT. Up to 40% of pediatric patients who receive OLT suffer from post transplantation allergy, autoimmunity, and immune-mediated disorders (PTAA). PTAA is more common after liver and heart transplantations than kidney transplantations. Potential contributing factors for the increased frequency of PTAA after OLT include the age of the patients, the prolonged use of tacrolimus and the reduced regulatory immune function with a shift towards a TH2 immune response. Better understanding of the mechanisms leading to the development of PTAA after OLT will also improve the management of these conditions.

Background: Inherited defects in the function of the purine nucleoside phosphorylase (PNP) enzyme can cause severe T cell immune deficiency and early death from infection, autoimmunity, or malignancy. In addition, more than 50% of patients suffer diverse non-infectious neurological complications. However the cause for the neurological abnormalities are not known. Objectives: Differentiate induced pluripotent stem cells (iPSC) from PNP-deficient patients into neuronal cells to better understand the effects of impaired purine metabolism on neuronal development. Methods: Sendai virus was used to generate pluripotent stem cells from PNP-deficient and healthy control lymphoblastoid cells. Cells were differentiated into neuronal cells through the formation of embryoid bodies. Results: After demonstration of pluripotency, normal karyotype, and retention of the PNP deficiency state, iPSC were differentiated into neuronal cells. PNP-deficient neuronal cells had reduced soma and nuclei size in comparison to cells derived from healthy controls. Spontaneous apoptosis, determined by Caspase-3 expression, was increased in PNP-deficient cells. Conclusions: iPSC from PNP-deficient patients can be differentiated into neuronal cells, thereby providing an important tool to study the effects of impaired purine metabolism on neuronal development and potential treatments. Statement of novelty: We report here the first generation and use of neuronal cells derived from induced pluripotent stem cells to model human PNP deficiency, thereby providing an important tool for better understanding and management of this condition.

Introduction: Adenosine deaminase (ADA) deficiency is a systemic metabolic disorder characterized by severe immune and non-immune abnormalities and is often fatal in infancy. ADA deficiency can be ...

The noncanonical NF-κB pathway is implicated in diverse biological and immunological processes. Monoallelic C-terminus loss-of-function and gain-of-function mutations of NFKB2 have been recently identified as a cause of immunodeficiency manifesting with common variable immunodeficiency (CVID) or combined immunodeficiency (CID) phenotypes. Herein we report a family carrying a heterozygous nonsense mutation in NFKB2 (c.809G > A, p.W270*). This variant is associated with increased mRNA decay and no mutant NFKB2 protein expression, leading to NFKB2 haploinsufficiency. Our findings demonstrate that bona fide NFKB2 haploinsufficiency, likely caused by mutant mRNA decay and protein instability leading to the transcription and expression of only the wild-type allele, is associated with clinical immunodeficiency, although with incomplete clinical penetrance. Abnormal B cell development, hypogammaglobulinemia, poor antibody response, and abnormal noncanonical (but normal canonical) NF-κB pathway signaling are the immunologic hallmarks of this disease. This adds a third allelic variant to the pathophysiology of NFKB2-mediated immunodeficiency disorders.

Background: Inherited defects in adenosine deaminase (ADA) cause severe immune deficiency, which can be corrected by ADA enzyme replacement therapy (ERT). Additionally, ADA-deficient patients suffer from hearing impairment. We hypothesized that ADA-deficient (–/–) mice also exhibit hearing abnormalities and that ERT from an early age will improve the hearing and immune defects in these mice. Methods: Auditory brainstem evoked responses, organ weights, thymocytes numbers, and subpopulations, lymphocytes in peripheral blood as well as T lymphocytes in spleen were analyzed in ADA–/– and ADA-proficient littermate post-partum (pp). The cochlea was visualized by scanning electron microscopy (SEM). The effects of polyethylene glycol conjugated ADA (PEG-ADA) ERT or 40% oxygen initiated at 7 days pp on the hearing and immune abnormalities were assessed. Results: Markedly abnormal hearing thresholds responses were found in ADA–/– mice at low and medium tone frequencies. SEM demonstrated extensive damage to the cochlear hair cells of ADA–/– mice, which were splayed, short or missing, correlating with the hearing deficits. The hearing defects were not reversed when hypoxia in ADA–/– mice was corrected. Progressive immune abnormalities were detected in ADA–/– mice from 4 days pp, initially affecting the thymus followed by peripheral lymphocytes and T cells in the spleen. ERT initiated at 7 days pp significantly improved the hearing of ADA–/– mice as well as the number of thymocytes and T lymphocytes, although not all normalized. Conclusions: ADA deficiency is associated with hearing deficits and damage to cochlear hair cells. Early initiation of ERT improves the hearing and immune abnormalities.

Abnormal alveolar macrophages (AM) are found in chronic obstructive pulmonary disease, asthma, cystic fibrosis, and adenosine deaminase deficiency (ADA(-/-)). There is no specific treatment strategy to compensate for these innate immune abnormalities. Recent findings suggest AMs are of early embryonic or fetal origin. Pluripotent stem cells (PSCs) as a source of embryonic-derived AMs for therapeutic use in acute and chronic airway diseases has yet to be investigated.To determine if embryonic Myb(-/-) alveolar-like macrophages have therapeutic value on pulmonary transplantation in acute and chronic airway diseases.Directed differentiation of murine PSCs was used in factor-defined media to produce expandable embryonic macrophages conditioned to an alveolar-like phenotype with granulocyte-macrophage colony-stimulating factor. AMs were partially depleted in mice to create an acute lung injury. To model a chronic lung disease, ADA(-/-) mice were used. Alveolar-like macrophages were intratracheally transplanted to the injured animals and therapeutic potential was determined.The differentiation protocol is highly efficient and adaptable to human PSCs. The PSC macrophages are phenotypically like AMs both functionally and by ligand marker characterization. They engulf bacteria and apoptotic cells and are better phagocytes than bone marrow-derived macrophages. In vivo, these macrophages remain in healthy airways for at least 4 weeks, can engulf neutrophils during acute lung injury, enhance pulmonary tissue repair, and promote survival in ADA(-/-) mice. Animals receiving the macrophages do not develop abnormal pathology or teratomas.PSCs are a reliable source to produce therapeutically active alveolar-like macrophages to treat airway disease.

Allergic, also known as atopic, diseases are a large group of conditions often involving IgE-mediated immune responses to environmental antigens (allergens), which commonly present as allergic rhinitis, atopic dermatitis, or asthma. It was previously suggested that autoimmune (AI) and allergic diseases would be mutually exclusive. Yet in recent years accumulating epidemiological data, advances in the understanding the complexities of the Th-1 and Th-2 immune responses, as well as lessons from primary and acquired immune abnormalities indicate that allergies and AI can coexist. Appreciation of the overlap in the pathogenesis of allergies and AI suggests that lessons in the management of one disorder might also be applicable to the other. Here we review some of the epidemiological, mechanistic, and genetic evidence linking AI with various allergic diseases.

Recent years have been marked by an increase in the number of gene defects identified among patients with primary immunodeficiency disease and a better appreciation of the mechanisms responsible for the associated impairment in immune regulation. These advances can be translated into an improved identification of patients with primary immune deficiencies and many other immune abnormalities, where polygenic and nongenetic factors might also contribute to the phenotype. Importantly, some of these advances can be used to generate novel immune checkpoint inhibitors and are likely to influence the development of additional immune modifiers that will assist in patients’ management.

Inherited defects in the ubiquitous adenosine deaminase (ADA) enzyme disrupt the function of the immune system as well as many other organs and tissues. Some patients may also suffer from kidney damage. Here we report on an ADA-deficient patient who was treated with ADA replacement therapy from infancy and at 6 years of age developed acute kidney failure, thrombocytopenia, and severe anemia. A kidney biopsy demonstrated mesangiolysis and occlusion of kidney loops by erythrocytes and platelet aggregates, which is consistent with hemolytic-uremic syndrome (HUS). There was no evidence of exposure to Shiga toxins, nor were any complement abnormalities detected. The kidney function improved following hemodialysis. Our report demonstrates the increased susceptibility of ADA-deficient patients to develop HUS and expands the nonimmune abnormalities associated with ADA deficiency. This further emphasizes the vigilance required when caring for such patients. Statement of novelty: Here we provide the first detailed clinical and histological characterization of hemolytic-uremic syndrome developing in an ADA-deficient patient.

In recent years, increasing numbers of patients with primary immune deficiency (PID) are being recognized as also suffering from cardiovascular system (CVS) abnormalities. These CVS defects might be explained by infectious or autoimmune etiologies, as well as by the role of specific genes and the immune system in the development and function of CVS tissues. Here, we provide the first comprehensive review of the clinical, potentially pathogenic mechanisms, and the management of PID, as well as the associated immune and CVS defects. In addition to some well-known associations of PID with CVS abnormalities, such as DiGeorge syndrome and CHARGE anomaly, we describe the cardiac defects associated with Omenn syndrome, calcium channel deficiencies, DNA repair defects, common variable immunodeficiency, Roifman syndrome, various neutrophil/macrophage defects, FADD deficiency, and HOIL1 deficiency. Moreover, we detail the vascular abnormalities recognized in chronic mucocutaneous candidiasis, chronic granulomatous disease, Wiskott–Aldrich syndrome, Schimke immuno-osseus dysplasia, hyper-IgE syndrome, MonoMAC syndrome, and X-linked lymphoproliferative disease. In conclusion, the expanding spectrum of PID requires increased alertness to the possibility of CVS involvement as an important contributor to the diagnosis and management of these patients.

Background: IVIG-SN is a modern intravenous immunoglobulin with multiple pathogen elimination steps. This clinical trial in patients with primary immunodeficiency (PID) was designed to evaluate the safety, efficacy, and tolerability of this product in adults and children. Methods: Forty-four patients with PID were treated with IVIG-SN for 12 months. IgG trough levels and pharmacokinetics of IVIG-SN were evaluated as well as efficacy and safety according to standard FDA guidelines. Results: Overall, a total of 572 IVIG-SN infusions were administered according to either a 21- or a 28-day schedule. IgG trough levels during the treatment period ranged from 823.00 to 902.77 mg/dL, respectively, and half-life in serum of the administered IgG was 43.45 ± 30.25 days. There were no deaths and no adverse events leading to withdrawal from the study. Of all infusions administered, only 137 (24%) were temporally associated with an adverse event (AE). The upper bound for the 95% CI for the frequency of infusions temporally associated with an AE was 29.2%. Drug-related AEs were predominantly mild, and there were no acute serious bacterial infections during the study. Efficacy was also demonstrated by low rates of missed work, school, or daycare days (mean 2.6 days); unscheduled visits to physicians (mean 1.7); and therapeutic antibiotic use (mean 15 days). Conclusion: IVIG-SN is effective in preventing infections and is safe and well tolerated. Statement of novelty: This efficacy and toxicity trial was conducted using a new IVIG preparation.

Immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX) syndrome is a rare primary immunodeficiency caused by inherited defects in the FOXP3 gene that impair regulatory T cells. IPEX syndrome can be cured by hematopoietic stem cell transplantation (HSCT) from HLA-matched unrelated donors (MUD); however, the best conditioning prior to HSCT for IPEX syndrome is not known. Here we report on a patient suffering from IPEX syndrome, including immune-mediated colitis and membranous nephropathy, without polyendocrinopathy, caused by a novel mutation in the Forkhead domain of the FOXP3 gene. The patient's symptoms resolved following MUD HSCT after myeloablative conditioning performed at 16 months of age. The patient is clinically well, 3 years after HSCT, with robust immune reconstitution and fully engrafted. The lack of extensive autoimmune damage might have contributed to the patient's favourable outcome following MUD HSCT with myeloablative conditioning. Statement of novelty: We describe a novel mutation in the FOXP3 gene causing IPEX syndrome and the correction of IPEX syndrome with bone marrow transplant from a HLA-matched unrelated donor following myeloablative conditioning.

Background: Cartilage-hair hypoplasia (CHH), caused by mutations in the ribonuclease mitochondrial RNA-processing (RMRP) gene, is associated with diverse immune abnormalities including combined immune deficiency (CID). Most patients with CHH are managed with supportive measurements, while few have received allogeneic hematopoietic stem cell transplantations (HSCT). The progression of the immune abnormalities and the impact of HSCT in patients with CHH and CID have not been well characterized.Methods: The clinical and laboratory findings of 2 siblings diagnosed in infancy with CHH and CID due to the common 70A>G mutation in RMRP, including the effects of HSCT performed in 1 of them, were compared.Results: Both patients suffered from recurrent respiratory infections at early age with reduced T cells numbers and responses. Patient 1 immune function continued to deteriorate leading to HSCT from an HLA-matched sibling at 4.5 years of age. The patient suffered acute and chronic graft versus host disease of the ...

To describe the prevalence, natural course, outcome, and risk factors of post-transplant de novo allergy and autoimmunity.A cross-sectional, cohort study of all children (18 years) who underwent a solid-organ transplantation, between 2000 and 2012, in a single transplant center, with a follow-up period of 6 months or more post-transplant and without history of allergy or immune-mediated disorder pretransplant.A total of 626 eligible patients were screened, and 273 patients (160 males; 59%) met the inclusion criteria; this included 111 liver, 103 heart, 52 kidney, and 7 multivisceral recipients. Patients were followed for a median period of 3.6 years. A total of 92 (34%) patients (42 males, 46%) developed allergy or autoimmune disease after transplantation, with a high prevalence among liver (41%), heart (40%), and multivisceral (57%) transplant recipients compared with kidney recipients (4%; P .001). Post-transplant allergies included eczema (n = 44), food allergy (22), eosinophilic gastrointestinal disease (11), and asthma (28). Autoimmunity occurred in 18 (6.6%) patients, presenting mainly as autoimmune cytopenia (n = 10). In a multivariate analysis, female sex, young age at transplantation, family history of allergy, Epstein-Barr virus infection, and elevated eosinophil count6 months post-transplantation were associated with an increased risk for allergy or autoimmunity. Two patients (0.7%) died from autoimmune hemolytic anemia and hemophagocytic lymphohistiocytosis, and 52 episodes of post-transplant allergy, autoimmunity, and immune-mediated disorders (37%) did not improve over time.Allergy and autoimmunity are common in pediatric liver, heart, and multivisceral transplant recipients and pose a significant health burden. Further studies are required to clarify the mechanisms behind this post-transplant immune dysregulation.

The nuclear factor kappa-light-chain-enhancer of activated B-cells (NFκB) family of transcription factors plays an instrumental role in human immunity and lymphoid organ development. Inherited defects affecting these factors or their regulation are associated with increased susceptibility to infections, as well as non-immune abnormalities. Hematopoietic stem cell transplantations (HSCT) have been shown to correct the immune abnormalities in a few patients with NFκB pathway defects. Here we review the pre-HSCT characteristics, as well as the HSCT and outcome of 35 patients who received HSCT for NFκB defects. Twenty-three patients (65.7%) were reported to have survived HSCT. Survival was higher among patients with X-linked ectodermal dysplasia and immunodeficiency (XL-EDA-ID), and those with CARD11-BCL10-MALT1 (CBM) complex defects, in comparison to patients with autosomal dominant ectodermal dysplasia and immunodeficiency (AD-EDA-ID) and IKBKB defects. Survival following myeloablative conditioning was simi...

Purpose: Inherited defects in the adenosine deaminase (ADA) enzyme can cause severe combined immune deficiency (SCID) and systemic abnormalities. Management options for ADA-deficient patients include enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT), and gene therapy (GT). Here, we describe the long-term benefits of these treatments. Methods: Survival, infections, systemic sequelae, and laboratory assessments were recorded for all ADA-deficient SCID patients, managed at a single center since 1985, who survived 5 or more years following treatment. Results: Of 20 ADA-deficient patients, the 8 (40%) who survived 5 or more years (range 6–29.5years, median 14years) were included in the study. Among the long-term survivors, two patients were treated exclusively with ERT, five underwent HSCT (three from HLA-matched sibling donors, two from HLA-mismatched related donors), and one received GT. The long-term survivors often suffered from recurrent respiratory infections; however, opportunistic infections occurred in only one patient. Systemic sequelae included lung disease such as bronchiectasis and asthma (four patients), neurologic abnormalities (six patients), metabolic disturbances (two patients), allergy and autoimmunity (six patients), and neoplasms (three patients). Normal CD4+ T cell numbers and function, as well as antibody production, were usually observed after HSCT and GT, but not after ERT. Late deaths occurred in two patients at 15 and 25years after HSCT, respectively, and were attributed to respiratory failure. Conclusions: ADA-deficient patients commonly suffer from long-term complications, emphasizing the need for improved management and for multi-disciplinary follow-up.

Purine nucleoside phosphorylase (PNP) deficiency is an autosomal recessive genetic disorder of the purine salvage pathway, associated with a variable extent of immunodeficiency. Here, we report a PNP-deficient patient who presented early in life with clinical and laboratory characteristics of severe combined immunodeficiency, including severe infections, marked T-and B-cell deficiency, lack of lymphocyte response to mitogenic stimulation, monoclonal T-cell receptors representation and the absence of T-cell receptor excision circles and Kappa-receptor excision circles. The patient carried homozygote mutation at the PNP gene that putatively led to aberrant splicing, allowing normal and abnormally spliced products from the mutant alleles. We suggest that the aberrant slice site was used preferentially over the normal slice site in some cells correlating with the severity of disease.

WOS: 000398771800023, PubMed ID: 27697500, Background: X-linked hyper-IgM syndrome (XHIGM) is a primary immunodeficiency with high morbidity and mortality compared with those seen in healthy subjects. Hematopoietic cell transplantation (HCT) has been considered a curative therapy, but the procedure has inherent complications and might not be available for all patients. Objectives: We sought to collect data on the clinical presentation, treatment, and follow-up of a large sample of patients with XHIGM to (1) compare long-term overall survival and general well-being of patients treated with or without HCT along with clinical factors associated with mortality and (2) summarize clinical practice and risk factors in the subgroup of patients treated with HCT. Methods: Physicians caring for patients with primary immunodeficiency diseases were identified through the Jeffrey Modell Foundation, United States Immunodeficiency Network, Latin American Society for Immunodeficiency, and Primary Immune Deficiency Treatment Consortium. Data were collected with a Research Electronic Data Capture Web application. Survival from time of diagnosis or transplantation was estimated by using the Kaplan-Meier method compared with log-rank tests and modeled by using proportional hazards regression. Results: Twenty-eight clinical sites provided data on 189 patients given a diagnosis of XHIGM between 1964 and 2013; 176 had valid follow-up and vital status information. Sixty-seven (38%) patients received HCT. The average follow-up time was 8.5 +/- 7.2 years (range, 0.1-36.2 years). No difference in overall survival was observed between patients treated with or without HCT (P = .671). However, risk associated with HCT decreased for diagnosis years 1987-1995; the hazard ratio was significantly less than 1 for diagnosis years 1995-1999. Liver disease was a significant predictor of overall survival (hazard ratio, 4.9; 95% confidence limits, 2.2-10.8; P < .001). Among survivors, those treated with HCT had higher median Karnofsky/Lansky scores than those treated without HCT (P < .001). Among patients receiving HCT, 27 (40%) had graft-versus-host disease, and most deaths occurred within 1 year of transplantation. Conclusion: No difference in survival was observed between patients treated with or without HCT across all diagnosis years (1964-2013). However, survivors treated with HCT experienced somewhat greater well-being, and hazards associated with HCT decreased, reaching levels of significantly less risk in the late 1990s. Among patients treated with HCT, treatment at an early age is associated with improved survival. Optimism remains guarded as additional evidence accumulates., Jeffrey Modell Foundation; National Institutes of Health Office of Rare Diseases, National Center for Advancing Translational Sciences and National, Institute of Allergy and Infectious Disease [U54 AI 082973, R13AI094943], Supported by a grant from Jeffrey Modell Foundation (to M.d.l.M.). The Primary Immune Deficiency Treatment Consortium (PIDTC) is supported by the National Institutes of Health Office of Rare Diseases, National Center for Advancing Translational Sciences and National, Institute of Allergy and Infectious Disease grants U54 AI 082973 and R13AI094943.

Adenosine deaminase (ADA) deficiency is a rare, autosomal-recessive systemic metabolic disease characterized by severe combined immunodeficiency (SCID). The treatment of choice for ADA-deficient SCID (ADA-SCID) is hematopoietic stem cell transplant from an HLA-matched sibling donor, although

Ab-producing plasma cells (PCs) serve as key participants in countering pathogenic challenges as well as being contributors to autoimmune and malignant disorders. Thus far, only a limited number of PC–specific markers have been identified. The characterization of the unique variable lymphocyte receptor (VLR) Abs that are made by evolutionarily distant jawless vertebrates prompted us to investigate whether VLR Abs could detect novel PC antigens that have not been recognized by conventional Abs. Here, we describe a monoclonal lamprey Ab, VLRB MM3, that was raised against primary multiple myeloma cells. VLRB MM3 recognizes a unique epitope of the CD38 ectoenzyme that is present on plasmablasts and PCs from healthy individuals and on most, but not all, multiple myelomas. Binding by the VLRB MM3 Ab coincides with CD38 dimerization and NAD glycohydrolase activity. Our data demonstrate that the lamprey VLRB MM3 Ab is a unique reagent for the identification of plasmablasts and PCs, with potential applications in the diagnosis and therapeutic intervention of PC or autoimmune disorders.

Background CD3δ deficiency is a fatal form of severe combined immunodeficiency that can be cured by hematopoietic stem cell transplantation (HSCT). The presence of a thymus loaded with T-cell progenitors in patients with CD3δ deficiency may require special considerations in choosing the regimen of conditioning and the type of HSCT. Objectives To study the outcome of CD3δ deficiency by using various modalities of stem cell transplantation. Methods We analyzed data on 13 patients with CD3δ deficiency who underwent HSCT in 7 centers. HSCT was performed by using different sources of donor stem cells as well as various conditioning regimens. Results One patient received stem cells from a matched related donor and survived after a second transplant, needing substantial conditioning in order to engraft. Only 2 of 7 other patients who received a mismatched related donor transplant survived; 2 of them had no conditioning, whereas the others received various combinations of conditioning regimens. Engraftment of T cells in the survivors appears incomplete. Three other patients who received stem cells from a matched unrelated donor survived and enjoyed full immune reconstitution. Two patients received unrelated cord blood without conditioning. One of them has had a partial but stable engraftment, whereas the other engrafted well but is only 12 months after HSCT. We also report here for the first time that patients with CD3δ deficiency can present with typical features of Omenn syndrome. Conclusions HSCT is a successful treatment for patients with CD3δ deficiency. The small number of patients in this report prevents definitive statements on the importance of survival factors, but several are suggested: (1) HLA-matched donor transplants are associated with superior reconstitution and survival than are mismatched donor transplants; (2) substantial conditioning appears necessary; and (3) early diagnosis and absence of opportunistic infections may affect outcome.

Severe combined immunodeficiency (SCID) is fatal in infancy unless corrected with allogeneic bone marrow transplants (BMT), preferably from a family-related genotypically HLA-identical donor (RID) or phenotypically HLA-matched family donor (PMD). For the majority of SCID patients, such donors are not available; Therefore, parents who are HLA-haploidentical donors (HID) or HLA-matched unrelated donors (MUD) have been used. MUD BMT are associated with increased frequency of acute graft versus host disease, which can be controlled by high doses of steroids. HID BMT are associated with increased frequency of short- and long-term graft failure, need for repeated transplants, fatal pneumonitis, impaired immune reconstitution, and long-term complications, contributing to lower survival. In conclusion, the excellent long-term survival, immune reconstitution, and normal quality of life after MUD BMT suggests that in the absence of RID or PMD, MUD BMT should be offered for patients suffering from SCID.

BACKGROUND: Cytotoxic-T-lymphocyte-antigen-4 (CTLA-4) is a negative immune regulator. Heterozygous CTLA4 germline mutations can cause a complex immune dysregulation syndrome in humans. OBJECTIVE: To characterize the penetrance, the clinical features and the best treatment options in 133 CTLA4 mutation carriers. METHODS: Genetics, clinical features, laboratory values, and outcome of treatment options were assessed in a worldwide cohort of CTLA4 mutation carriers. RESULTS: We identified 133 subjects from 54 unrelated families carrying 45 different heterozygous CTLA4 mutations, including 28 previously undescribed mutations. Ninety mutation carriers were considered affected, suggesting the clinical penetrance of at least 67%; median age of onset was 11 years, and mortality rate within affected mutation carriers was 16% (n=15). Main clinical manifestations included hypogammaglobulinemia (84%), lymphoproliferation (73%), autoimmune cytopenia (62%), respiratory- (68%), gastrointestinal- (59%), or neurological features (29%). Eight affected mutation carriers developed lymphoma, three gastric cancer. An EBV association was found in six malignancies. CTLA4 mutations were associated with lymphopenia and decreased T-, B-, and NK-cell counts. Successful targeted therapies included the application of CTLA-4-fusion-proteins, mTOR-inhibitors, and hematopoietic stem cell transplantation. EBV reactivation occurred in two affected mutation carriers under immunosuppression. CONCLUSIONS: Affected mutation carriers with CTLA-4 insufficiency may present in any medical specialty. Family members should be counseled, as disease manifestation may occur as late as age 50. EBV- and CMV-associated complications must be closely monitored. Treatment interventions should be coordinated in clinical trials.

Objective: To report a case of calcineurin-induced pain syndrome (CIPS) in a child undergoing his second hematopoietic stem cell transplant (HSCT). Case Summary: A 6.1-year-old child received cyclosporine and methotrexate for acute graft-versus-host disease (aGVHD) prophylaxis after his first HSCT for acute myeloblastic leukemia. Amlodipine was given for the treatment of hypertension. Symptoms of CIPS were not observed. After the second HSCT at the age of 6.7 years, the child received cyclosporine (target trough whole blood cyclosporine concentration range 150–200 μg/L). starting on day −3, and mycophenolate mofetil for aGVHD prophylaxis. With the first cyclosporine dose, the patient complained of leg pain that was most severe during the cyclosporine infusion. Analgesic agents and a change from intravenous to oral administration of cyclosporine were Ineffective In controlling the pain. Magnetic resonance imaging findings on day 10 showed periosteal soft tissue changes and mild bone marrow edema of the femora and tibiae. Tacrolimus was substituted for cyclosporine on day 20; on day 21 amlodipine was initiated to manage hypertension. Trough whole blood tacrolimus concentrations ranged from 1.7 to 6.2 μg/L. Pain was reduced in seventy by day 29 and completely resolved once tacrolimus was discontinued on day 42. In this case, CIPS was considered to be probably associated with cyclosporine according to the Naranjo probability scale. Discussion: CIPS is hypothesized to result from calcineurin-induced vascular changes that disturb bone perfusion and permeability, leading to intraosseous vasoconstriction and bone manow edema. In our patient, symptoms were most acute during the infusion, when whole blood cyclosporine concentrations were likely to be the highest. Our patient's symptoms were resolved when tacrolimus was substituted for cyclosporine and amlodipine was initiated. Conclusions: interventions aimed at reducing pain associated with CIPS may include the initiation of calcium-channel blocker therapy and conversion to an alternative calcineurin inhibitor.

Little information is currently available on the outcome and the long-term restoration of immune function in infants with combined immunodeficiency and residual T cells (T+ CID) treated by BMT. We prospectively followed patients with T+ CID who received matched unrelated donor BMT at our center. Engraftment, immune reconstitution and transplant-related complications were recorded. Humoral and cellular immunity were evaluated. Ten patients with combined immune deficiency who had more than 1,000 circulating T cells/mul were designated as having T+ CID. They were diagnosed at a mean age of 9.7 months and received a matched unrelated donor BMT at the mean age of 17.4 months. All 10 patients are alive and well at a mean of 110 months after transplant. All patients have evidence of full hemopoietic engraftment and robust immune function. We have shown here that matched unrelated donor BMT is highly effective in curing patients with T+ CID. This mode of treatment should be preferred for patients with T+ CID when a related identical donor is not available.

Children with primary immune deficiency (PID) who receive hematopoietic stem cell transplantation (HSCT) often suffer from graft-versus-host disease (GVHD), which is commonly treated with corticosteroids (CS). CS may cause hypertension, development of cardiac chamber hypertrophy (CCH), and left ventricular outflow tract obstruction (LVOTO). We followed the development of CCH and LVOTO by serial echocardiograms in 10 children with PID before and 6 to 12 weeks after HSCT, and correlated their development with age of transplant, GVHD, use of CS and hypertension. CCH developed in all 4 children transplanted before 1 year of age who received high dose CS treatment for grade III or IV acute GVHD (aGVHD), but not in the 6 children who were transplanted at later ages or who had not received high-dose CS (P = .07). Significant correlation (P < .002) was found between CCH and blood pressure measurements that deviated above the 99th percentile. One child also suffered from severe LVOTO. CCH and LVOTO improved when CS treatment was discontinued and blood pressure normalized. We conclude that following HSCT, young children who suffer from aGVHD, treated with high CS doses, and have excessive hypertension are at risk of developing CCH.

Defects in adenosine deaminase enzyme cause severe immunodeficiency. Without enzyme replacement or allogeneic bone marrow transplantation, patients often suffer fatal infection in infancy. Adenosine deaminase is expressed ubiquitously; deficiency may affect various organs, including the brain. Neurologic abnormalities occur in some adenosine deaminase-deficient patients, mostly in association with infection or after bone marrow transplantation. Three cases with significant neurologic abnormalities, including hypotonia, head lag, nystagmus, difficulty in focusing gaze, seizure disorder, and moderate-severe developmental delay but with no evidence of infection or transplant-related medication toxicity are presented. Computed tomographic scans and cranial MRI revealed volume loss and abnormalities of basal ganglia and thalamus, which may reflect accelerated nerve cell death or altered stimulation of adenosine receptors. Detailed neurologic and neuroimaging evaluation should be performed for all patients with adenosine deaminase deficiency upon diagnosis, to identify potentially significant brain lesions.

Inherited immune deficiencies are a heterogeneous group of diseases that can be either isolated, with the immune defect being the exclusive manifestation, or associated with other abnormalities. We report on two sisters, born to consanguineous parents of Sri-Lankan descent, who presented in infancy with immunodeficiency, gonadal dysgenesis, and fatal lung fibrosis. Immune studies demonstrated combined humoral and cellular abnormalities including reduced immunoglobulin production, an absence of lymphoid tissue, markedly reduced T-lymphocyte numbers and function and reduced newly thymus-derived T-cells. Both infants succumbed to rapidly progressive lung fibrosis. Autopsy showed dysgenetic gonads bearing no discernible oocytes. In both, karyotypes were normal female (46,XX). Comparative genome hybridization and analysis of genes known to be associated with severe immune defects in infancy or gonadal dysgenesis showed no abnormality. The distinct findings in these two sisters have not been reported before and thus suggest a hitherto unknown autosomal recessive condition that includes immune dysfunction, gonadal dysgenesis, and pulmonary fibrosis.

The association of cartilage hair hypoplasia (CHH) with severe combined immunodeficiency (SCID) has been known for more than three decades. Bone marrow transplantation (BMT) remains the only effective treatment that might cure SCID. Surprisingly little has been reported on the experience with BMT in CHH. We report here survival and long-term reconstitution of immunity after BMT in three patients with CHH. Regardless of whether a related human leukocyte antigen-matched or unrelated matched donors were used as the source of BMT, all patients are alive and well 5-20 years after BMT. Engraftment appears robust with most cells of donors origin. Repeated evaluation of the immune system showed normal cellular and humoral immunity. Our results should encourage the use of BMT in patients with CHH who have profound immunodeficiency.

Defects in purine nucleoside phosphorylase (PNP) enzyme activity result in abnormal nucleoside homeostasis, severe T cell immunodeficiency, neurological dysfunction, and early death. Protein transduction domain (PTD) can transfer molecules into cells and may help restore PNP activity in cases of PNP deficiency. However, long-term use of PTD to replace enzymes in animal models or patients has not previously been described. We fused human PNP to the HIV-TAT PTD and found that the fusion with TAT changed the retention and distribution of PNP in PNP-deficient mice. TAT induced rapid intracellular delivery of PNP into tissues, including the brain, prevented urinary excretion of PNP, and protected PNP from neutralizing antibodies, resulting in significant extension of the enzyme’s biological activity in vivo. Frequent TAT-PNP injections in PNP-deficient mice corrected the metabolic disorder and immune defects with no apparent toxicity. TAT-PNP remained effective over 24 weeks of treatment, resulting in continued improvement in immune function and extended survival. Our data demonstrate that TAT changes the properties of PNP in vivo and that long-term intracellular delivery of PNP by TAT corrects PNP deficiency in mice. We provide evidence to promote further use of PTD to treat diseases that require repeated intracellular enzyme or protein delivery.

Severe combined immunodeficiency (SCID) is a heterogeneous group of diseases that are invariably fatal in infancy unless treated by hematopoietic stem cell replacement. For many years we have worked to better manage patients affected by SCID through rapid and accurate diagnosis followed by treatment aimed at achieving long-lasting immune reconstitution. By extensive immunological, biochemical, and genetic studies of patient samples, and with the realization of differences between human and murine T cell development, we have successfully been able to identify some of the molecular defects causing SCID. Among these discoveries, we described the first mutated signal transduction protein in T cells (ZAP-70); the first genetic defect leading to SCID and autoimmune phenomena (IL2R alpha); and, recently, the critical importance of CD3delta in the development of T cells. Our efforts have significantly advanced the understanding of the role of some of the signal-transducing proteins in T cell maturation and function. This review summarizes several of these discoveries and some of their impact on our understanding of T cells development, function, and homeostasis in humans.

When a high titre inhibitor develops in a patient with haemophilia, attempts are made to eradicate it through immune tolerance induction therapy (ITI) involving the frequent and regular administration of factor, usually for months to years. ITI is successful in only two thirds of patients prompting investigators to explore alternate regimens to use in haemophiliacs failing conventional ITI. Rituximab is an anti-CD20 monoclonal antibody, which has shown promise in the treatment of B-cell-mediated disorders. We developed a protocol for the use of rituximab in haemophilia A (HA) patients failing conventional ITI or in those haemophiliacs where the likelihood of success of conventional ITI is poor. Patients receive 375 mg m(-2) of intravenous rituximab weekly for 4 weeks followed by monthly (up to 5 months) until inhibitor disappearance and establishment of normal FVIII pharmacokinetics (recovery and half-life). Patients are concurrently placed on recombinant FVIII (100 U kg(-1) day(-1)). We have placed five haemophiliacs (four children with severe HA, and one adult with mild HA) on this protocol. In three patients (two with severe HA and one with mild HA) inhibitors disappeared although in neither severe haemophiliac did FVIII pharmacokinetics completely normalize. The fourth patient had a significant drop in inhibitor titres although not a complete disappearance of the inhibitor. All four of these patients ceased bleeding following rituximab. The fifth patient had no response to rituximab. This non-responding patient was not placed on concurrent FVIII. Our five cases suggest that rituximab may hold promise in the eradication of inhibitors. Prospective randomized studies are required to determine the value of this agent in inhibitor management.

Purine nucleoside phosphorylase (PNP) deficiency is an autosomal recessive metabolic disorder characterized by severe combined immunodeficiency and by complex neurologic symptomatology including ataxia, developmental delay, and spasticity. Herein we report severe marrow dysplasia in a patient with PNP deficiency. Drug-related marrow dysfunction was unlikely, and marrow virological studies were negative. A preleukemic myelodysplastic syndrome was also unlikely due to normal marrow CD34+ cells, colony growth in clonogenic assay of marrow mononuclear cells, apoptosis rate, and Fas expression on marrow nucleated cells, as well as morphologic improvement of the marrow dysplasia after normal red blood cell transfusion. The patient's marrow stroma showed hypersensitivity to irradiation and undetectable PNP enzyme activity similar to peripheral lymphocytes. This is the first report of PNP deficiency associated with increased lymphocyte and marrow stromal sensitivity to irradiation. We conclude that marrows from patients with PNP deficiency might have hypersensitivity to irradiation and can develop dysplastic morphology, caused either directly or indirectly by the inherited enzymatic defect.