an X-linked recessive immunodeficiency and lymphoproliferative disease caused by mutation in the SH2 domain protein 1A gene (SH2D1A) on Xq; characterized by defective cellular or humoral immune response to Epstein-Barr virus; manifestations include fulminant infectious mononucleosis, B-cell malignancies, and hypogammaglobulinemia. SYN: Duncan disease, Duncan syndrome, lymphoproliferative syndrome, X-linked lymphoproliferative disease.