Two related boys who died from fulminant infectious mononucleosis were diagnosed with X-linked lymphoproliferative disease type 1 (XLP-1). Family screening (n=17) identified 6 female mutation carriers and 2 more XLP-1 patients in whom, despite recurrent infections, agammaglobulinemia, and Hodgkin's Disease, the genetic basis had been unknown; demonstrating that awareness and early genetic testing are crucial to reveal underlying primary immunodeficiencies and improve outcome. Furthermore, XLP should be included routinely in the differential diagnosis of severe hypogammaglobulinemia and/or lymphoma in males.
