MAGT1 gene mutation causes myositis and CD127 expression downregulation

Abstract X-linked immunodeficiency with Magnesium defect, Epstein-Barr virus infection, and Neoplasia (XMEN) is a primary immune deficiency caused by mutations in MAGT1 and is characterized by chronic infection with Epstein-Barr virus (EBV), CD4 lymphopenia, severe chronic viral infections, and defective T-lymphocyte activation. Herein, we described an XMEN patient carrying a MAGT1 p.Arg331* mutation that presented with prominent muscle involvement. The PET-CT and lower limbs MRI showed diffuse muscle inflammation. Histopathology staining revealed the infiltrated lymphocytes were stained with CD3, CD20, and EBER. We monitored the patient’s in-depth immunophenotype at the first visit and after two months of oral Mg 2+ supplementation. We noticed obviously decreased CD127 expression in CD4 + T cells, which could be reversed by Mg 2+ supplementation. Our findings suggested that the decreased CD127 expression may be an additional biomarker of XMEN.