As a form of severe combined immunodeficiency (SCID), Janus kinase 3 (JAK3) deficiency can be fatal during severe infections in children, especially after inoculation of live-attenuated vaccines. We report a unique case of JAK3 deficiency with two compound heterozygous JAK3 mutations complicated by disseminated Bacille Calmette-Guérin (BCG) disease and Pneumocystis pneumonia. A 5-month-old Chinese girl presented with recurring fever and productive cough after BCG vaccination and ineffective antibiotic treatment. Chest CT demonstrated bilateral infiltrations, enlarged mediastinal and axillary lymph nodes, and hypoplasia of the thymus. Mycobacterium tuberculosis and Pneumocystis jirovecii were detected from blood samples by sequencing. Acid-fast bacilli were also found from the sputum aspirate and gastric aspirate. Lymphocyte subset analyses indicated T-B+NK- immunodeficiency, and gene sequencing identified two heterozygous missense mutations (one unreported globally) in the Janus homology 7 (JH7) domain of JAK3. The patient received rifampicin, isoniazid, ethambutol, and trimethoprim/sulfamethoxazole and was discharged after improvements but against advice. The patient died at 13 months of age due to severe infections and hepatic damage. SCID should be recognized before inoculation of live-attenuated vaccines in children. Newborn screening for SCID is advocated. Further investigations are needed to better understand the pathogenicity of the variants and molecular mechanism of the JH7 domain of JAK3.

Human Inborn Errors of Immunity (IEIs) are clinically and genetically heterogeneous group of diseases, with relatively mild clinical course or severe types that can be life-threatening. Severe combined immunodeficiency (SCID) is the most severe form of IEIs, which is caused by monogenic defects that impair the proliferation and function of T, B, and NK cells. According to the most recent report by the International Union of Immunological Societies (IUIS), SCID is caused by mutations in IL2RG, JAK3, FOXN1, CORO1A, PTPRC, CD3D, CD3E, CD247, ADA, AK2, NHEJ1, LIG4, PRKDC, DCLRE1C, RAG1 and RAG2 genes. The targeted next-generation sequencing (TNGS) workflow based on Ion AmpliSeq™ Primary Immune Deficiency Research Panel was designed for sequencing 264 IEI-related genes on Ion S5™ Sequencer. Herein, we present 21 disease-causing variants (12 novel) which were identified in 22 patients in eight different SCID genes. Next-generation sequencing allowed a rapid and an accurate diagnosis SCID patients.

Severe combined immunodeficiency (SCID) is fatal if not treated with immune reconstitution. In Egypt, T- B+ SCID accounts for 38·5% of SCID diagnoses. An accurate genetic diagnosis is essential for choosing appropriate treatment modalities and for offering genetic counseling to the patient's family. The objectives of this study were to describe the clinical, immunological and molecular characteristics of a cohort of twenty Egyptian patients with T- B+ SCID. The initial diagnosis (based on clinical features and flow cytometry) was followed by molecular investigation (whole-exome sequencing). All patients had the classic clinical picture for SCID, including failure to thrive (n = 20), oral candidiasis (n = 17), persistent diarrhea (n = 14), pneumonia (n = 13), napkin dermatitis (n = 10), skin rash (n = 7), otitis media (n = 3) and meningitis (n = 2). The onset of manifestations was at the age of 2·4 ± 1·6 months and diagnosis at the age of 6·7 ± ·5 months, giving a diagnostic delay of 4·3 months. JAK3 gene variants were most frequent (n = 12) with three novel variants identified, followed by IL2Rγ variants (n = 6) with two novel variants. IL7Rα and CD3ε variants were found once, with a novel variant each. T- B+ NK- SCID accounted for approximately 90% of the Egyptian patients with T- B+ SCID. Of these T- B+ NK- SCID cases, 60% were autosomal recessive syndromes caused by JAK3 mutations and 30% were X-linked syndromes. It might be useful to sequence the JAK3 gene (i.e. targeted Sanger sequencing) in all T- B+ SCID patients, especially after X-linked SCID has been ruled out. Hence, no more than 10% of T- B+ SCID patients might require next-generation for a molecular diagnosis.

Severe combined immunodeficiency (SCID) represents one of the most severe forms of primary immunodeficiency (PID) disorders characterized by impaired cellular and humoral immune responses. Here, we report the clinical, immunological, and molecular findings in 57 patients diagnosed with SCID from India. Majority of our patients (89%) presented within 6 months of age. The most common clinical manifestations observed were recurrent pneumonia (66%), failure to thrive (60%), chronic diarrhea (35%), gastrointestinal infection (21%), and oral candidiasis (21%). Hematopoietic Stem Cell Transplantation (HSCT) is the only curative therapy available for treating these patients. Four patients underwent HSCT in our cohort but had a poor survival outcome. Lymphopenia (absolute lymphocyte counts/μL <2,500) was noted in 63% of the patients. Based on immunophenotypic pattern, majority of the cases were T-B- SCID (39%) followed by T-B+ SCID (28%). MHC class II deficiency accounted for 10.5% of our patient group. A total of 49 patients were molecularly characterized in this study and 32 novel variants were identified in our cohort. The spectrum of genetic defects in our cohort revealed a wide genetic heterogeneity with the major genetic cause being RAG1/2 gene defect (n = 12) followed by IL2RG (n = 9) and JAK3 defects (n = 9). Rare forms of SCID like Purine nucleoside phosphorylase (PNP) deficiency, reticular dysgenesis, DNA-Protein Kinase (DNA-PKcs) deficiency, six cases of MHC class II deficiency and two ZAP70 deficiency were also identified in our cohort. Fourteen percent of the defects still remained uncharacterized despite the application of next generation sequencing. With the exception of MHC class II deficiency and ZAP70 deficiency, all SCID patients had extremely low T cell receptor excision (TRECs) (<18 copies/μL).

Mutations in the Janus Kinase 3 (JAK3) gene cause an autosomal recessive form of severe combined immunodeficiency (SCID) usually characterized by the absence of both T and NK cells, but preserved numbers of B lymphocytes (T-B+NK-SCID). The detection of larger (>100 bp) genomic duplications or deletions can be more difficult to be detected by PCR-based methods or standard NGS protocols, and a broad range of mutation detection techniques are necessary. We report four unrelated Italian patients (two females and two males) with SCID phenotype. Protein expression, functional studies, molecular analysis by standard methods and NGS, and transcripts studies were performed to obtain a definitive diagnosis. Here, we describe four JAK3-deficient patients from four unrelated families. The first patient is homozygous for the known c.1951 C>T mutation causing the amino acidic change p.R651W. The other two patients, originating from the same small Italian town, resulted compound heterozygotes for the same g.15410_16542del deletion and two different novel mutations, g.13319_13321delTTC and c.933T>G (p.F292V), respectively. The fourth patient was compound heterozygous for the novel mutations p.V599G and p.W709R. Defective STAT5 phosphorylation after IL2 or IL15 stimulation corroborated the mutation pathogenicity. Concerning g.15410_16542del mutation, probably due to an unequal homologous recombination between Alu elements of JAK3 gene, microsatellites analysis revealed that both unrelated Pt2 and Pt3 and their carrier family members shared the same haplotype. These data support the hypothesis of a founder effect for the g.15410_16542del mutation that might have inherited in both unrelated families from the same ancient progenitor. Different molecular techniques are still required to obtain a definitive diagnosis of AR-SCID particularly in all cases in which a monoallelic mutation is found by standard mutation scanning methods.