Identification of a novel MAGT1 mutation supports a diagnosis of XMEN disease.

XMEN (X-linked immunodeficiency with magnesium defect) is caused by loss-of-function mutations in MAGT1 which is encoded on the X chromosome. The disorder is characterised by CD4 lymphopenia, severe chronic viral infections and defective T-lymphocyte activation. XMEN patients are susceptible to Epstein-Barr virus infections and persistently low levels of intracellular Mg2+. Here we describe a patient that presented with multiple recurrent infections and a subsequent diffuse B-cell lymphoma. Molecular genetic analysis by exome sequencing identified a novel hemizygous MAGT1 nonsense mutation c.1005T>A (NM_032121.5) p.(Cys335*), confirming a diagnosis of XMEN deficiency. Follow-up immunophenotyping was performed by antibody staining and flow cytometry; proliferation was determined by 3H-thymidine uptake after activation by PHA and anti-CD3. Cytotoxic natural killer cell activity was assessed with K562 target cells using the NKTESTTM assay. While lymphocyte populations were superficially intact, B cells were largely naive with a reduced memory cell compartment. Translated NKG2D was absent on both NK and T cells in the proband, and normally expressed in the carrier mother. In vitro NK cell activity was intact in both the proband and his mother. This report adds to the growing number of identified XMEN cases, raising awareness of a, still rare, X-linked immunodeficiency.

Progressive B Cell Loss in Revertant X-SCID.

We report the case of a patient with X-linked severe combined immunodeficiency (X-SCID) who survived for over 20 years without hematopoietic stem cell transplantation (HSCT) because of a somatic reversion mutation. An important feature of this rare case included the strategy to validate the pathogenicity of a variant of the IL2RG gene when the T and B cell lineages comprised only revertant cells. We studied the X-inactivation of sorted T cells from the mother to show that the pathogenic variant was indeed the cause of his SCID. One interesting feature was a progressive loss of B cells over 20 years. CyTOF (cytometry time of flight) analysis of bone marrow offered a potential explanation of the B cell failure, with expansions of progenitor populations that suggest a developmental block. Another interesting feature was that the patient bore extensive granulomatous disease and skin cancers that contained T cells, despite severe T cell lymphopenia in the blood. Finally, the patient had a few hundred T cells on presentation but his TCRs comprised a very limited repertoire, supporting the important conclusion that repertoire size trumps numbers of T cells.

X-Linked Hyper IgM Syndrome Presenting with Recurrent Tuberculosis-a Case Report.

The hyper IgM syndromes are a group of rare primary immunodeficiency disorders. Currently 6 classes of HIGM are described. X-linked HIGM is also called the type 1 HIGM is the commonest variant in which children present in early infancy with features of combined immunodeficiency. Tuberculosis is a very rare presentation as a presenting symptom in HIGM. Here, we describe a child with XHIGM with recurrent tuberculosis.

The IL-2RG R328X nonsense mutation allows partial STAT-5 phosphorylation and defines a critical region involved in the leaky-SCID phenotype.

In addition to their detection in typical X-linked severe combined immunodeficiency, hypomorphic mutations in the interleukin (IL)-2 receptor common gamma chain gene (IL2RG) have been described in patients with atypical clinical and immunological phenotypes. In this leaky clinical phenotype the diagnosis is often delayed, limiting prompt therapy in these patients. Here, we report the biochemical and functional characterization of a nonsense mutation in exon 8 (p.R328X) of IL2RG in two siblings: a 4-year-old boy with lethal Epstein-Barr virus-related lymphoma and his asymptomatic 8-month-old brother with a Tlow B+ natural killer (NK)+ immunophenotype, dysgammaglobulinemia, abnormal lymphocyte proliferation and reduced levels of T cell receptor excision circles. After confirming normal IL-2RG expression (CD132) on T lymphocytes, signal transducer and activator of transcription-1 (STAT-5) phosphorylation was examined to evaluate the functionality of the common gamma chain (γc ), which showed partially preserved function. Co-immunoprecipitation experiments were performed to assess the interaction capacity of the R328X mutant with Janus kinase (JAK)3, concluding that R328X impairs JAK3 binding to γc . Here, we describe how the R328X mutation in IL-2RG may allow partial phosphorylation of STAT-5 through a JAK3-independent pathway. We identified a region of three amino acids in the γc intracellular domain that may be critical for receptor stabilization and allow this alternative signaling. Identification of the functional consequences of pathogenic IL2RG variants at the cellular level is important to enable clearer understanding of partial defects leading to leaky phenotypes.

X-Linked Severe Combined Immunodeficiency and Hepatoblastoma: A Case Report and Review of Literature.

Severe combined immunodeficiency is an inherited disease with profoundly defective T cells, B cells, and natural killer cells. X-linked severe combined immunodeficiency is the most common form. In this report, we describe a 4-month-old male infant who was admitted to our hospital with progressive breathlessness and abdominal mass. He was diagnosed with hepatoblastoma and presented a pneumocystis jirovecii pneumonia at the beginning of chemotherapy. Definitive diagnosis of X-linked severe combined immunodeficiency was established by DNA analysis of the interleukin 2 receptor gamma chain gene. This case is the first report which describes an X-linked severe combined immunodeficiency patient with hepatoblastoma.

Identification of IL2RG and CYBB mutations in two Chinese primary immunodeficiency patients by whole-exome sequencing.

BACKGROUND: Primary immunodeficiency diseases are a group of genetic disorders that lead to increased propensity to a variety of infections, sometimes with fatal outcomes. METHOD: In this study, whole-exome sequencing (WES) was used to identify mutations in two patients suspected of having primary immunodeficiency. Sanger sequencing was used to confirm the results in the patients and their family. RESULT: One patient was diagnosed as X-linked severe combined immunodeficiency (X-SCID) and another patient as X-linked chronic granulomatous disease (X-CGD) by WES. Sequencing analysis of IL2RG gene revealed a novel mutation (c.794T>A, p.I265N) and CYBB gene revealed a missense mutation (c.935T>A, p.M312K). DISCUSSION AND CONCLUSION: This study identifies one novel mutation in the IL2RG gene and another, previously described mutation in the CYBB genes. It is the first report establishing a diagnosis of X-SCID and X-CGD using WES in Chinese patients.

Acute Myeloid Leukemia in a Patient With X-linked Severe Combined Immunodeficiency.

Severe combined immunodeficiency (SCID) is a defect in the differentiation and function of T cells. An increased malignancy risk, mainly lymphatic malignancy, has been described in patients with SCID. We report a patient with X-linked SCID who developed acute myeloid leukemia, derived from the recipient with somatic NRAS mutation 4 months after cord blood transplantation (CBT). Loss of heterozygosity phenomenon of the recipient at 6q14 locus was observed at 2 months post-CBT and progressed to 6q deletion (6q-) chromosome abnormality. Somatic NRAS mutation was detected at 3 months post-CBT. Thus, 6q- and NRAS mutation were strongly associated with the leukemic transformation in our patient.

The role of MAGT1 in genetic syndromes.

Disturbances in magnesium homeostasis, often linked to altered expression and/or function of magnesium channels, have been implicated in a plethora of diseases. This review focuses on magnesium transporter 1 (MAGT1), as recently described changes in this gene have further extended our understanding of the role of magnesium in human health and disease. The identification of genetic changes and their functional consequences in patients with immunodeficiency revealed that magnesium and MAGT1 are key molecular players for T cell-mediated immune responses. This led to the description of XMEN (X-linked immunodeficiency with magnesium defect, Epstein Barr Virus infection, and neoplasia) syndrome, for which Mg2+ supplementation has been shown to be beneficial. Similarly, the identification of a copy-number variation (CNV) leading to dysfunctional MAGT1 in a family with atypical ATRX syndrome and skin abnormalities, suggested that the MAGT1 defect could be responsible for the cutaneous problems. On the other hand, recent genetic investigations question the previously proposed role for MAGT1 in intellectual disability. Understanding the molecular basis of the involvement of magnesium and its channels in human pathogenesis will improve opportunities for Mg2+ therapies in the clinic.

Identification of a novel mutation in MAGT1 and progressive multifocal leucoencephalopathy in a 58-year-old man with XMEN disease.

XMEN disease (X-linked immunodeficiency with Magnesium defect, Epstein-Barr virus infection and Neoplasia) is a novel primary immune deficiency caused by mutations in MAGT1 and characterised by chronic infection with Epstein-Barr virus (EBV), EBV-driven lymphoma, CD4 T-cell lymphopenia, and dysgammaglobulinemia [1]. Functional studies have demonstrated roles for magnesium as a second messenger in T-cell receptor signalling [1], and for NKG2D expression and consequently NK- and CD8 T-cell cytotoxicity [2]. 7 patients have been described in the literature; the oldest died at 45 years and was diagnosed posthumously [1-3]. We present the case of a 58-year-old Caucasian gentleman with a novel mutation in MAGT1 with the aim of adding to the phenotype of this newly described disease by detailing his clinical course over more than 20 years.

X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection, and neoplasia disease: a combined immune deficiency with magnesium defect.

PURPOSE OF REVIEW: To describe the role of the magnesium transporter 1 (MAGT1) in the pathogenesis of 'X-linked immunodeficiency with magnesium defect, Epstein-Barr virus (EBV) infection, and neoplasia' (XMEN) disease and its clinical implications. RECENT FINDINGS: The magnesium transporter protein MAGT1 participates in the intracellular magnesium ion (Mg) homeostasis and facilitates a transient Mg influx induced by the activation of the T-cell receptor. Loss-of-function mutations in MAGT1 cause an immunodeficiency named 'XMEN syndrome', characterized by CD4 lymphopenia, chronic EBV infection, and EBV-related lymphoproliferative disorders. Patients with XMEN disease have impaired T-cell activation and decreased cytolytic function of natural killer (NK) and CD8 T cells because of decreased expression of the NK stimulatory receptor 'natural-killer group 2, member D' (NKG2D). Patients may have defective specific antibody responses secondary to T cell dysfunction, but B cells have not been shown to be directly affected by mutations in MAGT1. SUMMARY: XMEN disease has revealed a novel role for free intracellular magnesium in the immune system. Further understanding of the MAGT1 signaling pathway may lead to new diagnostic and therapeutic approaches.

XMEN disease: a new primary immunodeficiency affecting Mg2+ regulation of immunity against Epstein-Barr virus.

Epstein-Barr virus (EBV) is an oncogenic gammaherpesvirus that infects and persists in 95% of adults worldwide and has the potential to cause fatal disease, especially lymphoma, in immunocompromised hosts. Primary immunodeficiencies (PIDs) that predispose to EBV-associated malignancies have provided novel insights into the molecular mechanisms of immune defense against EBV. We have recently characterized a novel PID now named "X-linked immunodeficiency with magnesium defect, EBV infection, and neoplasia" (XMEN) disease characterized by loss-of-function mutations in the gene encoding magnesium transporter 1 (MAGT1), chronic high-level EBV with increased EBV-infected B cells, and heightened susceptibility to EBV-associated lymphomas. The genetic etiology of XMEN disease has revealed an unexpected quantitative role for intracellular free magnesium in immune functions and has led to novel diagnostic and therapeutic strategies. Here, we review the clinical presentation, genetic mutation spectrum, molecular mechanisms of pathogenesis, and diagnostic and therapeutic considerations for this previously unrecognized disease.

[Combination of multiple displacement amplification with short tandem repeat polymorphismin preimplantation genetic diagnosis].

OBJECTIVE: To explore the application of multiple displacement amplification (MDA) combined with short tandem repeats (STRs) in preimplantation genetic diagnosis (PGD). METHODS: MDA was applied to amplify the whole genome of a single cell and to retrieve and assemble the highly heterogeneous STR loci among human population. Haplotype analytic system was established with aiming at diagnosis of the single gene diseases by selecting the STR loci located within the pathogenic genes or on both bounding sides of the pathogenic genes. At the same time, allele specific amplification, PCR-reverse dot-blotting hybridization methods and gene sequencing methods were employed for direct detection of the pathogenic genes. The STR loci located at related chromosomes were selected to carry out allele number analysis on the basis of chromosome number and structural abnormality. RESULTS: In the study, 12 PGD systems were set up including 6 different monogenic diseases (spinal muscular atrophy, Duchenne muscular dystrophy, X-linked chronic granulomatous disease, osteopetrosis, achondroplasia, X-linked severe combined immunodeficiency), Robertsonian translocations, α-thalassemia combined with Robertsonian translocation, α- and ß-double thalassemia, ß-thalassemia with HLA typing and DMD with HLA typing. Then 44 PGD cycles were performed for 35 couples with different kinds of inherited diseases, which resulted in 20 healthy liveborns (12 singletons and 4 twins) and 5 ongoing pregnancies. The clinical pregnancy rate was 47.7% (21/44) per PGD cycle. The overall diagnostic rate was 94.6% (367/388). The MDA failed in 3.6% (14/388) single blastomeres. The amplification rate of the subsequent PCR was 97.1% and the average allele drop out (ADO) rate was 12.6% (range: 0-47.5%). CONCLUSION: The application of MDA combined with STRs provided a generic PGD approach for different genetic disorders, especially for simultaneous diagnosis of two or more hereditary statuses. The method could greatly shorten the time of developing PGD system of new diseases, which broadens the indications of PGD.

Non-infectious lung disease in patients with adenosine deaminase deficient severe combined immunodeficiency.

Adenosine deaminase deficiency is a disorder of purine metabolism manifesting severe combined immunodeficiency (ADA-SCID) and systemic abnormalities. Increased levels of the substrate deoxyadenosine triphosphate (dATP) lead to immunodeficiency and are associated in a murine model with pulmonary insufficiency. We compared a cohort of patients with ADA-SCID and X-linked SCID and found that despite similar radiological and respiratory findings, positive microbiology is significantly less frequent in ADA-SCID patients (p < 0.0005), suggesting a metabolic pathogenesis for the lung disease. Clinicians should be aware of this possibility and correct metabolic abnormalities either through enzyme replacement or haematopoietic stem cell transplant, in addition to treating infectious complications.

Disseminated BCG infection mimicking metastatic nasopharyngeal carcinoma in an immunodeficient child with a novel hypomorphic NEMO mutation.

BACKGROUND: Nuclear factor-κB essential modulator (NEMO) deficiency is a developmental and immunological disorder. The genetic and phenotypic correlation has been described. METHODS: We report a unique clinical presentation and the identification of a novel missense mutation in the NEMO gene in a 3-year-old boy with bacillus Calmette-Guerin (BCG) infection. RESULTS: The patient presented with fever, cervical lymphadenopathy, and abnormal anti-Epstein-Barr virus (EBV) antibody titers, suggestive of EBV-related diseases including chronic active EBV infection, X-linked lymphoproliferative syndrome, or nasopharyngeal carcinoma. Although the biopsy specimen from a nasopharyngeal lesion was initially diagnosed as squamous cell carcinoma, this was changed to disseminated BCG infection involving the nasopharynx, multiple systemic lymph nodes, and brain. A novel mutation (designated D311E) in the NEMO gene, located in the NEMO ubiquitin-binding (NUB) domain, was identified as the underlying cause of the immunodeficiency. Impaired immune responses which are characteristic of patients with NEMO deficiency were demonstrated. The patient underwent successful unrelated bone marrow transplantation at 4.9 years of age. CONCLUSION: This study suggests the importance of the NUB domain in host defense against mycobacteria. The unique presenting features in our patient indicate that a hypomorphic NEMO mutation can be associated with atypical pathological findings of the epithelial tissues in patients with BCG infection.

Chronic noninfectious necrotizing granulomas in a child with Nijmegen breakage syndrome.

Nijmegen breakage syndrome (NBS) is a chromosomal breakage disorder with characteristic physical features, chromosomal instability, and combined immunodeficiency. It is closely related to other chromosomal breakage disorders like ataxia telangiectasia. Noninfectious granulomatous inflammation refractory to treatment is a relatively common feature in ataxia telangiectasia. Herein we report a patient with NBS who developed chronic refractory necrotizing granulomatous ulcerations and review the pathophysiology of NBS and noninfectious granulomas in primary immunodeficiency syndromes.

[Disseminated BCG infection revealing X-linked severe combined immunodeficiency]. / BCGite disséminée révélant un déficit immunitaire combiné sévère lié à l'X.

BACKGROUND: Live attenuated Bacillus Calmette-Guérin (BCG) vaccine is rarely responsible for disseminated infection. We report a case of X-linked severe combined immunodeficiency (SCID) revealed by a disseminated skin infection. PATIENTS AND METHODS: A 4-month-old baby was hospitalized for prolonged gastroenteritis. He was in poor general condition, with prolonged fever, oral and gluteal candidiasis and purple nodules associated with ulceration of the BCG scar. The absence of a thymus, T-cells and NK-cells, and the presence of nonfunctional B-lymphocytes led to a diagnosis of SCID. Biopsies of nodules revealed a dermal infiltrate without necrosis. A Ziehl-Neelson stain was highly positive and the culture grew Mycobacterium bovis. Treatment consisted of a four-drug antibiotic regimen directed against M. bovis combined with gamma interferon, immunoglobulins and antibiotic prophylaxis by cotrimoxazole and was followed by a haploid-identical bone marrow transplant without rejection at six months. The early death of the child's maternal uncle from sepsis suggested X-linked transmission, which was subsequently confirmed by genetic analysis. DISCUSSION: BCG vaccination can cause serious infections in immunocompromised subjects. Skin involvement is extremely rare but may be the first sign of SCID, of which the X-linked form is the most common and corresponds to a variety of mutations in the gene coding for the gamma chain common to several interleukin receptors. Genetic counselling is essential to identify female carriers and allow early antenatal diagnosis. Bone marrow transplantation is the only treatment.