B-cells absence in patients diagnosed as inborn errors of immunity: a registry-based study.

Hypogammaglobulinemia without B-cells is a subgroup of inborn errors of immunity (IEI) which is characterized by a significant decline in all serum immunoglobulin isotypes, coupled with a pronounced reduction or absence of B-cells. Approximately 80 to 90% of individuals exhibit genetic variations in Bruton's agammaglobulinemia tyrosine kinase (BTK), whereas a minority of cases, around 5-10%, are autosomal recessive agammaglobulinemia (ARA). Very few cases are grouped into distinct subcategories. We evaluated phenotypically and genetically 27 patients from 13 distinct families with hypogammaglobinemia and no B-cells. Genetic analysis was performed via whole-exome and Sanger sequencing. The most prevalent genetic cause was mutations in BTK. Three novel mutations in the BTK gene include c.115 T > C (p. Tyr39His), c.685-686insTTAC (p.Asn229llefs5), and c.163delT (p.Ser55GlnfsTer2). Our three ARA patients include a novel homozygous stop-gain mutation in the immunoglobulin heavy constant Mu chain (IGHM) gene, a novel frameshift mutation of the B-cell antigen receptor complex-associated protein (CD79A) gene, a novel bi-allelic stop-gain mutation in the transcription factor 3 (TCF3) gene. Three patients with agammaglobulinemia have an autosomal dominant inheritance pattern, which includes a missense variant in PIK3CD, a novel missense variant in PIK3R1 and a homozygous silent mutation in the phosphoinositide-3-kinase regulatory subunit (RASGRP1) gene. This study broadens the genetic spectrum of hypogammaglobulinemia without B-cells and presented a few novel variants within the Iranian community, which may also have implications in other Middle Eastern populations. Notably, disease control was better in the second affected family member in families with multiple cases.

A case of T-cell acute lymphoblastic leukemia in retroviral gene therapy for ADA-SCID.

Hematopoietic stem cell gene therapy (GT) using a γ-retroviral vector (γ-RV) is an effective treatment for Severe Combined Immunodeficiency due to Adenosine Deaminase deficiency. Here, we describe a case of GT-related T-cell acute lymphoblastic leukemia (T-ALL) that developed 4.7 years after treatment. The patient underwent chemotherapy and haploidentical transplantation and is currently in remission. Blast cells contain a single vector insertion activating the LIM-only protein 2 (LMO2) proto-oncogene, confirmed by physical interaction, and low Adenosine Deaminase (ADA) activity resulting from methylation of viral promoter. The insertion is detected years before T-ALL in multiple lineages, suggesting that further hits occurred in a thymic progenitor. Blast cells contain known and novel somatic mutations as well as germline mutations which may have contributed to transformation. Before T-ALL onset, the insertion profile is similar to those of other ADA-deficient patients. The limited incidence of vector-related adverse events in ADA-deficiency compared to other γ-RV GT trials could be explained by differences in transgenes, background disease and patient's specific factors.

Case report: Rapidly progressive neurocognitive disorder with a fatal outcome in a patient with PU.1 mutated agammaglobulinemia.

Introduction: PU.1-mutated agammaglobulinemia (PU.MA) represents a recently described autosomal-dominant form of agammaglobulinemia caused by mutation of the SPI1 gene. This gene codes for PU.1 pioneer transcription factor important for the maturation of monocytes, B lymphocytes, and conventional dendritic cells. Only six cases with PU.MA, presenting with chronic sinopulmonary and systemic enteroviral infections, have been previously described. Accumulating literature evidence suggests a possible relationship between SPI1 mutation, microglial phagocytic dysfunction, and the development of Alzheimer's disease (AD). Case description: We present a Caucasian female patient born from a non-consanguineous marriage, who was diagnosed with agammaglobulinemia at the age of 15 years when the immunoglobulin replacement therapy was started. During the following seventeen years, she was treated for recurrent respiratory and intestinal infections. At the age of 33 years, the diagnosis of celiac-like disease was established. Five years later progressive cognitive deterioration, unstable gait, speech disturbances, and behavioral changes developed. Comprehensive microbiological investigations were negative, excluding possible infective etiology. Brain MRI, 18FDG-PET-CT, and neuropsychological testing were suggestive for a diagnosis of a frontal variant of AD. Clinical exome sequencing revealed the presence of a novel frameshift heterozygous variant c.441dup in exon 4 of the SPI1 gene. Despite intensive therapy, the patient passed away a few months after the onset of the first neurological symptoms. Conclusion: We describe the first case of PU.MA patient presenting with a rapidly progressive neurocognitive deterioration. The possible role of microglial dysfunction in patients with SPI1 mutation could explain their susceptibility to neurodegenerative diseases thus highlighting the importance of genetic testing in patients with inborn errors of immunity. Since PU.MA represents a newly described form of agammaglobulinemia, our case expands the spectrum of manifestations associated with SPI1 mutation.

Gene regulation in inborn errors of immunity: Implications for gene therapy design and efficacy.

Inborn errors of immunity (IEI) present a unique paradigm in the realm of gene therapy, emphasizing the need for precision in therapeutic design. As gene therapy transitions from broad-spectrum gene addition to careful modification of specific genes, the enduring safety and effectiveness of these therapies in clinical settings have become crucial. This review discusses the significance of IEIs as foundational models for pioneering and refining precision medicine. We explore the capabilities of gene addition and gene correction platforms in modifying the DNA sequence of primary cells tailored for IEIs. The review uses four specific IEIs to highlight key issues in gene therapy strategies: X-linked agammaglobulinemia (XLA), X-linked chronic granulomatous disease (X-CGD), X-linked hyper IgM syndrome (XHIGM), and immune dysregulation, polyendocrinopathy, enteropathy, X-linked (IPEX). We detail the regulatory intricacies and therapeutic innovations for each disorder, incorporating insights from relevant clinical trials. For most IEIs, regulated expression is a vital aspect of the underlying biology, and we discuss the importance of endogenous regulation in developing gene therapy strategies.

X-Linked Lymphoproliferative Syndrome: A Spectrum of Clinical and Immunological Profile and Novel Pathogenic Variants from Chandigarh, India.

INTRODUCTION: X-linked lymphoproliferative syndrome (XLP) is a rare primary immune deficiency. Two types of XLP have been described: XLP-1 and XLP-2. METHODS: We found 7 patients with XLP (3 had XLP-1 and 4 had XLP-2) after reviewing the data from Pediatric Immunodeficiency Clinic from 1997 to 2021. RESULTS: Mean age at diagnosis was 3.8 years, and mean delay in diagnosis was 2.6 years. Five patients had recurrent episodes of infections. Four patients developed at least one episode of hemophagocytic lymphohistiocytosis (HLH) (2 with XLP-1 and 2 with XLP-2). Of these, 2 had recurrent HLH (both with XLP-2). Epstein-Barr virus (EBV) infection was detected in 2 (1 with XLP-1 and 1 with XLP-2). Both these patients had HLH. One child with XLP-2 had inflammatory bowel disease. Hypogammaglobulinemia was seen in 3 (2 with XLP-1 and 1 with XLP-2). Genetic analysis showed previously reported variants in 5, while 2 had novel variants (one in exon 7 of XIAP gene [c.1370dup p.Asn457Lysfs Ter16] and other had splice site variant in intron 1 of SH2D1A gene [c.138-2_138-1insG]). Episodes of HLH were managed with intravenous immunoglobulin (IVIg), methylprednisolone, oral prednisolone, cyclosporine, and rituximab. Inflammatory bowel disease was managed using oral prednisolone and azathioprine. One patient underwent haploidentical hematopoietic stem cell transplantation. One child with XLP-2 and WAS died because of fulminant pneumonia. DISCUSSION/CONCLUSIONS: XLP should be considered as a strong possibility in any patient with features of HLH, repeated infections with hypogammaglobulinemia, persistent EBV infection, and early-onset IBD.

What a Clinician Needs to Know About Genome Editing: Status and Opportunities for Inborn Errors of Immunity.

During the past 20 years, gene editing has emerged as a novel form of gene therapy. Since the publication of the first potentially therapeutic gene editing platform for genetic disorders, increasingly sophisticated editing technologies have been developed. As with viral vector-mediated gene addition, inborn errors of immunity are excellent candidate diseases for a corrective autologous hematopoietic stem cell gene editing strategy. Research on gene editing for inborn errors of immunity is still entirely preclinical, with no trials yet underway. However, with editing techniques maturing, scientists are investigating this novel form of gene therapy in context of an increasing number of inborn errors of immunity. Here, we present an overview of these studies and the recent progress moving these technologies closer to clinical benefit.

Enhanced CD19 activity in B cells contributes to immunodeficiency in mice deficient in the ICF syndrome gene Zbtb24.

Immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome is a rare autosomal recessive disorder characterized by DNA hypomethylation and antibody deficiency. It is caused by mutations in DNMT3B, ZBTB24, CDCA7, or HELLS. While progress has been made in elucidating the roles of these genes in regulating DNA methylation, little is known about the pathogenesis of the life-threatening hypogammaglobulinemia phenotype. Here, we show that mice deficient in Zbtb24 in the hematopoietic lineage recapitulate the major clinical features of patients with ICF syndrome. Specifically, Vav-Cre-mediated ablation of Zbtb24 does not affect lymphocyte development but results in reduced plasma cells and low levels of IgM, IgG1, and IgA. Zbtb24-deficient mice are hyper and hypo-responsive to T-dependent and T-independent type 2 antigens, respectively, and marginal zone B-cell activation is impaired. Mechanistically, Zbtb24-deficient B cells show severe loss of DNA methylation in the promoter region of Il5ra (interleukin-5 receptor subunit alpha), and Il5ra derepression leads to elevated CD19 phosphorylation. Heterozygous disruption of Cd19 can revert the hypogammaglobulinemia phenotype of Zbtb24-deficient mice. Our results suggest the potential role of enhanced CD19 activity in immunodeficiency in ICF syndrome.

Severe CD8+ T Lymphopenia in WHIM Syndrome Caused by Selective Sequestration in Primary Immune Organs.

Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome is an ultra-rare combined primary immunodeficiency disease caused by heterozygous gain-of-function mutations in the chemokine receptor CXCR4. WHIM patients typically present with recurrent acute infections associated with myelokathexis (severe neutropenia due to bone marrow retention of mature neutrophils). Severe lymphopenia is also common, but the only associated chronic opportunistic pathogen is human papillomavirus and mechanisms are not clearly defined. In this study, we show that WHIM mutations cause more severe CD8 than CD4 lymphopenia in WHIM patients and WHIM model mice. Mechanistic studies in mice revealed selective and WHIM allele dose-dependent accumulation of mature CD8 single-positive cells in thymus in a cell-intrinsic manner due to prolonged intrathymic residence, associated with increased CD8 single-positive thymocyte chemotactic responses in vitro toward the CXCR4 ligand CXCL12. In addition, mature WHIM CD8+ T cells preferentially home to and are retained in the bone marrow in mice in a cell-intrinsic manner. Administration of the specific CXCR4 antagonist AMD3100 (plerixafor) in mice rapidly and transiently corrected T cell lymphopenia and the CD4/CD8 ratio. After lymphocytic choriomeningitis virus infection, we found no difference in memory CD8+ T cell differentiation or viral load between wild-type and WHIM model mice. Thus, lymphopenia in WHIM syndrome may involve severe CXCR4-dependent CD8+ T cell deficiency resulting in part from sequestration in the primary lymphoid organs, thymus, and bone marrow.

Case Report: Interindividual variability and possible role of heterozygous variants in a family with deficiency of adenosine deaminase 2: are all heterozygous born equals?

Deficiency of adenosine deaminase 2 (DADA2) is a rare systemic autoinflammatory disease, typically with autosomal recessive inheritance, usually caused by biallelic loss of function mutations in the ADA2 gene. The phenotypic spectrum is broad, generally including fever, early-onset vasculitis, stroke, and hematologic dysfunction. Heterozygous carriers may show related signs and symptoms, usually milder and at an older age. Here we describe the case of two relatives, the proband and his mother, bearing an ADA2 homozygous pathogenic variant, and a heterozygous son. The proband was a 17-year-old boy with intermittent fever, lymphadenopathies, and mild hypogammaglobulinemia. He also had sporadic episodes of aphthosis, livedo reticularis and abdominal pain. Hypogammaglobulinemia was documented when he was 10 years old, and symptoms appeared in his late adolescence. The mother demonstrated mild hypogammaglobulinemia, chronic pericarditis since she was 30 years old and two transient episodes of diplopia without lacunar lesions on MRI. ADA2 (NM_001282225.2) sequencing identified both mother and son as homozygous for the c.1358A>G, p.(Tyr453Cys) variant. ADA2 activity in the proband and the mother was 80-fold lower than in the controls. Clinical features in both patients improved on anti-tumor necrosis factor therapy. An older son was found to be heterozygous for the same mutation post-mortem. He died at the age of 12 years due to a clinical picture of fever, lymphadenitis, skin rash and hypogammaglobulinemia evolving toward fatal multiorgan failure. Biopsies of skin, lymph nodes, and bone marrow excluded lymphomas and vasculitis. Despite being suspected of symptomatic carrier, the contribution of an additional variant in compound heterozygosity, or further genetic could not be ruled out, due to poor quality of DNA samples available. In conclusion, this familiar case demonstrated the wide range of phenotypic variability in DADA2. The search for ADA2 mutations and the assessment of ADA2 activity should be considered also in patients with the association of hypogammaglobulinemia and inflammatory conditions, also with late presentation and in absence of vasculitis. Furthermore, the clinical picture of the deceased carrier suggests a possible contribution of heterozygous pathogenic variants to inflammation.

Clinical applications of gene therapy for rare diseases: A review.

Rare diseases collectively exact a high toll on society due to their sheer number and overall prevalence. Their heterogeneity, diversity, and nature pose daunting clinical challenges for both management and treatment. In this review, we discuss recent advances in clinical applications of gene therapy for rare diseases, focusing on a variety of viral and non-viral strategies. The use of adeno-associated virus (AAV) vectors is discussed in the context of Luxturna, licenced for the treatment of RPE65 deficiency in the retinal epithelium. Imlygic, a herpes virus vector licenced for the treatment of refractory metastatic melanoma, will be an example of oncolytic vectors developed against rare cancers. Yescarta and Kymriah will showcase the use of retrovirus and lentivirus vectors in the autologous ex vivo production of chimeric antigen receptor T cells (CAR-T), licenced for the treatment of refractory leukaemias and lymphomas. Similar retroviral and lentiviral technology can be applied to autologous haematopoietic stem cells, exemplified by Strimvelis and Zynteglo, licenced treatments for adenosine deaminase-severe combined immunodeficiency (ADA-SCID) and ß-thalassaemia respectively. Antisense oligonucleotide technologies will be highlighted through Onpattro and Tegsedi, RNA interference drugs licenced for familial transthyretin (TTR) amyloidosis, and Spinraza, a splice-switching treatment for spinal muscular atrophy (SMA). An initial comparison of the effectiveness of AAV and oligonucleotide therapies in SMA is possible with Zolgensma, an AAV serotype 9 vector, and Spinraza. Through these examples of marketed gene therapies and gene cell therapies, we will discuss the expanding applications of such novel technologies to previously intractable rare diseases.

Updated Management Guidelines for Adenosine Deaminase Deficiency.

Inherited defects in the adenosine deaminase (ADA) gene typically cause severe combined immunodeficiency. In addition to infections, ADA-deficient patients can present with neurodevelopmental, behavioral, hearing, skeletal, lung, heart, skin, kidney, urogenital, and liver abnormalities. Some patients also suffer from autoimmunity and malignancies. In recent years, there have been remarkable advances in the management of ADA deficiency. Most ADA-deficient patients can be identified by newborn screening for severe combined immunodeficiency, which facilitates early diagnosis and treatment of asymptomatic infants. Most patients benefit from enzyme replacement therapy (ERT). Allogeneic hematopoietic cell transplantation from an HLA-matched sibling donor or HLA-matched family member donor with no conditioning is currently the preferable treatment. When matched sibling donor or matched family member donor is not available, autologous ADA gene therapy with nonmyeloablative conditioning and ERT withdrawal, which is reported in recent studies to result in 100% overall survival and 90% to 95% engraftment, should be pursued. If gene therapy is not immediately available, ERT can be continued for a few years, although its excessive cost might be prohibitive. The recent improved outcome of hematopoietic cell transplantation using HLA-mismatched family-related donors or HLA-matched unrelated donors, after reduced-intensity conditioning, suggests that such procedures might also be considered rather than continuing ERT for prolonged periods. Long-term follow-up will further assist in determining the optimal treatment approach for ADA-deficient patients.

Granulomatous inflammation and hypogammaglobulinemia: Clinical conundrum of familial hemophagocytic lymphohistiocytosis type 5.

Familial hemophagocytic lymphohistiocytosis (HLH) is an inherited disorder characterized by systemic hyperinflammation caused by an uncontrolled immune response mediated by T-lymphocytes, natural killer (NK) cells, and macrophages. Most children with familial HLH present within first 2 years of life and can have fatal disease unless hematopoietic stem cell transplant (HSCT) is performed (1). However, few patients may have late presentation and prolonged survival. With increasing awareness and facilities to identify HLH these disorders are being identified beyond infancy (2-4). Clinical and laboratory features are often similar to other primary immune deficiency diseases and pose diagnostic challenges (4-6). We report two patients who presented beyond the first decade of life with HLH, granulomatous inflammation, hypogammaglobulinemia, reduced B cells and were diagnosed to have familial HLH type 5 due to defect in STXBP2 gene.

Early onset is an indication of the severity of DADA2 disease.

OBJECTIVE: To find indicators of disease severity and factors of early remission in patients with deficiency of adenosine deaminase 2 (DADA2). METHODS: We enrolled six DADA2 patients from six families. Direct sequencing of adenosine deaminase 2 gene (ADA2) was performed by Sanger analysis. A literature review was conducted for articles regarding paediatric DADA2. RESULTS: We found that more organs were involved in early-onset (≤1 year of age) than in late-onset (>1 year of age) DADA2 patients had high level inflammatory responses, such as elevated ESR, SF, serum amyloid A and CRP. Disease severity was not significantly different from missense and frameshift mutation. Early administration of TNF inhibitor might result in better remission and reduce recurrence. In the literature, four articles describing 51 paediatric DADA2 patients were identified. We also found that fever, stroke, peripheral nervous system involvement, hypogammaglobulinaemia and hypertension were more frequent in early onset DADA2 patients. CONCLUSION: Early-onset DADA2 may be more severe. Early administration of TNF inhibitor can effectively reduce recurrence and quickly alleviate the disease.

Case Report: Consistent disease manifestations with a staggered time course in two identical twins affected by adenosine deaminase 2 deficiency.

Deficiency of adenosine deaminase 2 (DADA2) is an autosomal recessive disease associated with a highly variable clinical presentation, including vasculitis, immunodeficiency, and hematologic manifestations, potentially progressing over time. The present study describes the long-term evolution of the immuno-hematological features and therapeutic challenge of two identical adult twin sisters affected by DADA2. The absence of plasmatic adenosine deaminase 2 (ADA2) activity in both twins suggested the diagnosis of DADA2, then confirmed by genetic analysis. Exon sequencing revealed a missense (p.Leu188Pro) mutation on the paternal ADA2 allele. While, whole genome sequencing identified an unreported deletion (IVS6_IVS7del*) on the maternal allele predicted to produce a transcript missing exon 7. The patients experienced the disease onset during childhood with early strokes (Patient 1 at two years, Patient 2 at eight years of age), subsequently followed by other shared DADA2-associated features, including neutropenia, hypogammaglobulinemia, reduced switched memory B cells, inverted CD4:CD8 ratio, increased naïve T cells, reduced follicular regulatory T cells, the almost complete absence of NK cells, T-large granular cell leukemia, and osteoporosis. Disease evolution differed: clinical manifestations presented several years earlier and were more pronounced in Patient 1 than in Patient 2. Due to G-CSF refractory life-threatening neutropenia, Patient 1 successfully underwent an urgent hematopoietic stem cell transplantation (HSCT) from a 9/10 matched unrelated donor. Patient 2 experienced a similar, although delayed, disease evolution and is currently on anti-TNF therapy and anti-infectious prophylaxis. The unique cases confirmed that heterozygous patients with null ADA2 activity deserve deep investigation for possible structural variants on a single allele. Moreover, this report emphasizes the importance of timely recognizing DADA2 at the onset to allow adequate follow-up and detection of disease progression. Finally, the therapeutic management in these identical twins raises significant concerns as they share a similar phenotype, with a delayed but almost predictable disease evolution in one of them, who could benefit from a prompt definitive treatment like elective allogeneic HSCT. Additional data are required to assess whether the absence of enzymatic activity at diagnosis is associated with hematological involvement and is also predictive of bone marrow dysfunction, encouraging early HSCT to improve functional outcomes.

A Rare Autoinflammatory Disorder in a Pediatric Patient with Favorable Response to Etanercept: Sideroblastic Anemia with B Cell Immunodeficiency, Periodic Fevers, and Developmental Delay Syndrome.

Introduction: Sideroblastic anemia with B cell immunodeficiency, periodic fevers, and developmental delay (SIFD) syndrome is caused by biallelic TRNT1 mutations. TRNT1 gene encodes a CCA-adding tRNA nucleotidyl transferase enzyme. Mutant TRNT1 results in immunodeficiency and anemia in various degrees, accompanied by several organ involvement. Case Presentation: We present here a 15-month old male, demonstrated brittle hair, growth hormone deficiency, recurrent fever, arthritis, recurrent infections, mild anemia, and hypogammaglobulinemia. The patient did not respond to colchicine treatment, and after establishing SIFD diagnosis with the presence of homozygote c.948-949delAAinsGG (p.Lys317Glu) mutation in TRNT1 gene, we commenced monthly intravenous immunoglobulin replacement and weekly subcutaneous etanercept. A rapid resolution of fever episodes and infections occurred after initiation of this treatment regimen. Afterward, both anemia and growth parameters have improved during follow-up. Conclusion: SIFD syndrome should be considered in patients with recurrent fever, arthritis, and growth retardation even in the absence of severe anemia and prominent hypogammaglobulinemia.

Genotype-phenotype correlations in WHIM syndrome: a systematic characterization of CXCR4WHIM variants.

Warts, hypogammaglobulinemia, infections, myelokathexis (WHIM) syndrome is a rare primary immunodeficiency predominantly caused by heterozygous gain-of-function mutations in CXCR4 C-terminus. We assessed genotype-phenotype correlations for known pathogenic CXCR4 variants and in vitro response of each variant to mavorixafor, an investigational CXCR4 antagonist. We used cell-based assays to analyze CXCL12-induced receptor trafficking and downstream signaling of 14 pathogenic CXCR4 variants previously identified in patients with WHIM syndrome. All CXCR4 variants displayed impaired receptor trafficking, hyperactive downstream signaling, and enhanced chemotaxis in response to CXCL12. Mavorixafor inhibited CXCL12-dependent signaling and hyperactivation in cells harboring CXCR4WHIM mutations. A strong correlation was found between CXCR4 internalization defect and severity of blood leukocytopenias and infection susceptibility, and between AKT activation and immunoglobulin A level and CD4+ T-cell counts. This study is the first to show WHIM syndrome clinical phenotype variability as a function of both CXCR4WHIM genotype diversity and associated functional dysregulation. Our findings suggest that CXCR4 internalization may be used to assess the pathogenicity of CXCR4 variants in vitro and also as a potential WHIM-related disease biomarker. The investigational CXCR4 antagonist mavorixafor inhibited CXCL12-dependent signaling in all tested CXCR4-variant cell lines at clinically relevant concentrations.

Disease Progression of WHIM Syndrome in an International Cohort of 66 Pediatric and Adult Patients.

Warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) syndrome (WS) is a combined immunodeficiency caused by gain-of-function mutations in the C-X-C chemokine receptor type 4 (CXCR4) gene. We characterize a unique international cohort of 66 patients, including 57 (86%) cases previously unreported, with variable clinical phenotypes. Of 17 distinct CXCR4 genetic variants within our cohort, 11 were novel pathogenic variants affecting 15 individuals (23%). All variants affect the same CXCR4 region and impair CXCR4 internalization resulting in hyperactive signaling. The median age of diagnosis in our cohort (5.5 years) indicates WHIM syndrome can commonly present in childhood, although some patients are not diagnosed until adulthood. The prevalence and mean age of recognition and/or onset of clinical manifestations within our cohort were infections 88%/1.6 years, neutropenia 98%/3.8 years, lymphopenia 88%/5.0 years, and warts 40%/12.1 years. However, we report greater prevalence and variety of autoimmune complications of WHIM syndrome (21.2%) than reported previously. Patients with versus without family history of WHIM syndrome were diagnosed earlier (22%, average age 1.3 years versus 78%, average age 5 years, respectively). Patients with a family history of WHIM syndrome also received earlier treatment, experienced less hospitalization, and had less end-organ damage. This observation reinforces previous reports that early treatment for WHIM syndrome improves outcomes. Only one patient died; death was attributed to complications of hematopoietic stem cell transplantation. The variable expressivity of WHIM syndrome in pediatric patients delays their diagnosis and therapy. Early-onset bacterial infections with severe neutropenia and/or lymphopenia should prompt genetic testing for WHIM syndrome, even in the absence of warts.

A case of progressive multifocal leukoencephalopathy with hypogammaglobulinemia and a TCF3 mutation.

Progressive multifocal leukoencephalopathy (PML) is a rare and potentially fatal demyelinating disease of the central nervous system (CNS) caused by JC virus; it was previously seen predominantly in immunocompromised patients and those under intense immune suppression. Here, we report the case of a patient with PML with hypogammaglobulinemia and a heterozygous mutation in the TCF3 gene. As the TCF3 gene has been demonstrated to play an important role in the B cell differentiation process and the patient had no other medical history of the immune system, he was diagnosed with common variable immunodeficiency (CVID). To our knowledge, this is the first case of patient with a TCF3 gene deficiency and hypogammaglobulinemia who developed PML.

Targeted Gene Sanger Sequencing Should Remain the First-Tier Genetic Test for Children Suspected to Have the Five Common X-Linked Inborn Errors of Immunity.

To address inborn errors of immunity (IEI) which were underdiagnosed in resource-limited regions, our centre developed and offered free genetic testing for the most common IEI by Sanger sequencing (SS) since 2001. With the establishment of The Asian Primary Immunodeficiency (APID) Network in 2009, the awareness and definitive diagnosis of IEI were further improved with collaboration among centres caring for IEI patients from East and Southeast Asia. We also started to use whole exome sequencing (WES) for undiagnosed cases and further extended our collaboration with centres from South Asia and Africa. With the increased use of Next Generation Sequencing (NGS), we have shifted our diagnostic practice from SS to WES. However, SS was still one of the key diagnostic tools for IEI for the past two decades. Our centre has performed 2,024 IEI SS genetic tests, with in-house protocol designed specifically for 84 genes, in 1,376 patients with 744 identified to have disease-causing mutations (54.1%). The high diagnostic rate after just one round of targeted gene SS for each of the 5 common IEI (X-linked agammaglobulinemia (XLA) 77.4%, Wiskott-Aldrich syndrome (WAS) 69.2%, X-linked chronic granulomatous disease (XCGD) 59.5%, X-linked severe combined immunodeficiency (XSCID) 51.1%, and X-linked hyper-IgM syndrome (HIGM1) 58.1%) demonstrated targeted gene SS should remain the first-tier genetic test for the 5 common X-linked IEI.

Utility of targeted next generation sequencing for inborn errors of immunity at a tertiary care centre in North India.

Inborn errors of immunity (IEI) are a heterogeneous group of monogenic disorders that include primary immunodeficiency's and other disorders affecting different aspects of the immune system. Next-Generation Sequencing (NGS) is an essential tool to diagnose IEI. We report our 3-year experience in setting up facilities for NGS for diagnosis of IEI in Chandigarh, North India. We used a targeted, customized gene panel of 44 genes known to result in IEI. Variant analysis was done using Ion Reporter software. The in-house NGS has enabled us to offer genetic diagnoses to patients with IEI at minimal costs. Of 121 patients who were included pathogenic variants were identified in 77 patients. These included patients with Chronic Granulomatous Disease, Severe Combined Immune Deficiency, leukocyte adhesion defect, X-linked agammaglobulinemia, Ataxia Telangiectasia, Hyper-IgE syndrome, Wiskott Aldrich syndrome, Mendelian susceptibility to mycobacterial diseases, Hyper-IgM syndrome, autoimmune lymphoproliferative syndrome, and GATA-2 deficiency. This manuscript discusses the challenges encountered while setting up and running targeted NGS for IEI in our unit. Genetic diagnosis has helped our patients with IEI in genetic counselling, prenatal diagnosis, and accessing appropriate therapeutic options.