<h4>Background</h4>X-linked MAGT1 deficiency with increased susceptibility to EBV-infection and N-linked glycosylation (XMEN) disease is an inborn error of immunity (IEI) affecting the Magnesium Transporter 1 (<i>MAGT1)</i> gene. The gene discussed is MAGT1; the disease is X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection and neoplasia.