CD5 B-Cell Predominant Primary Immunodeficiency: Part of the Spectrum of MAGT1 Deficiency.

Background: Selective anti-polysaccharide antibody deficiency (SPAD) with CD5 B-cell predominance and autoimmune phenomena was identified in a male cohort first reported by Antall et al in 1999. The phenotypically likewise and genotypically identical X-linked immunodeficiency with magnesium defect, Epstein-Barr Virus infection, and neoplasia (XMEN) disease was defined as a novel primary immunodeficiency (PID) in 2011. Recent studies of the magnesium transporter 1 (MAGT1) gene mutation reveal glycosylation defects contributing to more phenotypic variance than the "XMEN" title pathologies. The updated title, "X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation defect," was proposed in 2020. Objectives: To reflect the patient population more accurately, a prospective classification update may consider MAGT1 glycobiological errors contributing to phenotypic variance but also pre-genetic testing era reports with CD5 B-cell predominance. Methods: Patient 1 from Antall et al presented at 28 years of age for further immunological evaluation of his CD5/CD19 B-cell predominance diagnosed at 5 years old. Design: Immune re-evaluation done through flow cytometry and next-generation sequencing. Results: Flow cytometry B-cell phenotyping revealed persistent CD5+CD19+ (93%). Flow cytometric histogram quantified reduced activator CD16+CD56+ natural killer and CD8+ T-cell receptor, Group 2, Member D (NKG2D) glycoprotein expression. A c.923-1_934 deletion loss of function mutation was identified in the MAGT1 gene. Conclusion: We suggest the novel PID XMEN, based on its CD5 B-cell predominance, had been discovered and reported over a decade earlier as CD5+ PID based on the MAGT1 mutation found in the same. We encourage consideration of combining these labels and recent findings to offer the most accurate classification of this disease.

IgM Deficiency Associated With Connexin Mutation in an 18-Year-old Male.

IgM deficiency is characterized by remarkably low serum levels of IgM with normal IgG and IgA levels. These patients clinically present with recurrent infections, autoimmune disorders, and malignancies. While unknown, the proposed mechanisms explain the pathophysiology as an issue due to impaired IgG antibody response. The connexin genes encode for gap junctional proteins where mutations can cause hearing deficits and immune dysregulation. We present a unique case of an 18-year-old patient with recurrent sinusitis, diagnosed connexin-26 mutation and an IgM deficiency. An 18-year-old male with chronic sinusitis, Marfanoid joint hypermobility syndrome, and sensorineural hearing loss due to connexin-26 deficiency with bilateral cochlear implants. This patient's mutation is a GJB2 deletion located on chromosome 13 which encodes for the connexin-26 protein. The patient experienced recurrent infections, and serum immunoglobulins showed a normal IgA (84 mg/dL; normal: 70-400 mg/dL), IgG (922 mg/dL; normal: 700-1600 mg/dL) and reduced IgM (26 mg/dL; normal: 40-230 mg/dL) levels. The patient was responsive to Mumps, Measles, Rubella, and Diphtheria vaccinations among others, consistent with SIGMD diagnoses. Antibody responses to polysaccharide antigens were absent. The leukocyte counts were within normal limits. His parents are connexin-26 deficient carriers, and his older brother was diagnosed with SIGMD. Connexin-26 has been identified with multiple immunological mechanisms. Although mutations of this gene have no direct tie to antibody formation in relation to IgM, the presence of these 2 pathologies in 1 patient is intriguing and may suggest a pathophysiologic connection. We describe the first case of connexin mutation with an IgM deficiency in an 18-year-old male.

Association of natural killer cell dysfunction and recurrent Stevens-Johnson syndrome in a pediatric patient.

Stevens-Johnson syndrome (SJS) is a debilitating condition involving the skin and mucous membranes. It is commonly the result of adverse drug reactions but can also be caused by infections. A predisposition to recurrent viral infections, such as in the case of natural killer (NK) cell dysfunction, may manifest with virally induced SJS. We present this case to suggest a possible association between NK cell dysfunction and recurrent SJS. An 11-year-old girl presents with recurring erythema, erosion, and ulceration of oral and vaginal mucosa. Small fluid-filled bumps would appear, leading to blistering and later sloughing of mucosal tissue, and bleeding would ensue. Seven separate episodes have occurred over an 8-year period, with each episode being preceded by symptoms of an upper respiratory infection. NK cell function assays were performed and NK cell phenotyping was ordered. NK cell assays showed decreased NK cell cytotoxicity at all ratios of K562 target cells. NK cell surface expression evaluation showed an immature phenotype but normal overall numbers of NK cells. NK cells are a pivotal part of the innate immune system, and, among other things, provide defense of viral infection. This case represents the manifestation of recurrent SJS as a result the lack of protection from viral illness, usually provided by NK cells in the healthy immune system.