MAGT1 (magnesium transporter 1) is an X-linked gene encoding a protein with dual roles in cellular function. Primarily, MAGT1 serves as an accessory component of the STT3B-containing oligosaccharyl transferase (OST) complex, which catalyzes N-glycosylation of nascent polypeptides 1. The protein facilitates glycosylation of acceptor sites near cysteine residues through oxidoreductase activity and substrate recognition functions 1. MAGT1 also mediates magnesium ion homeostasis, particularly in T lymphocytes and immune cells 2, with magnesium entry dependent on MAGT1 in neurons and other cell types 3. Mutations in MAGT1 cause X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection, and neoplasia (XMEN) syndrome 4, classified as both a primary immunodeficiency and congenital disorder of glycosylation 5. XMEN patients exhibit CD4+ T lymphocytopenia, inverted CD4/CD8 ratios, and increased susceptibility to EBV-associated malignancies 5. MAGT1 deficiency also predisposes to hemophagocytic lymphohistiocytosis (HLH) 6. Beyond immunodeficiency, MAGT1 loss dysregulates platelet cation homeostasis, accelerating arterial thrombosis and ischemic stroke through enhanced calcium influx and dysregulated signaling 7. Magnesium supplementation shows therapeutic benefit in managing XMEN disease 4.