Follow-up testing by flow cytometry revealed the canonical disruption in Natural Killer Group 2D (NKG2D) surface expression on CD8 T cells and NK cells, and clinical testing for congenital disorders of glycosylation (CDG) additionally verified the hallmark defect in glycosylation that underpins XMEN disease. Here, KLRK1 is linked to X-linked immunodeficiency with magnesium defect, Epstein-Barr virus infection and neoplasia.