MAGT1 and X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection and neoplasia: Furthermore, variants in the X-linked MAGT1 causing hypoglycosylation led to the re-classification of MAGT1 deficiency as a CDG, which was previously only associated with a primary immunodeficiency with a magnesium transport defect (XMEN) [42].