MAGT1 and diffuse large B-cell lymphoma: MAGT1 deficiency also termed XMEN disease (for X-linked immunodeficiency, magnesium defect, EBV infection, and neoplasia syndrome) is caused by hemizygous mutations in MAGT1. To date, 11 male patients with MAGT1 deficiency have been identified and all developed susceptibility to EBV infection with chronic viremia and B-cell lymphomas including Hodgkin and DLBCL (78–82).