noun. A type of immune disorder characterised by a reduction in all types of gamma globulins.

noun. an abnormally low concentration of gamma globulin in the blood and increased risk of infection

"The diagnosis might also be considered if there is a family history where relatives were affected by illnesses found in X-linked lymphoproliferative syndrome (XLP), such as fatal Epstein-Barr virus (EBV) infection, lymphoma or hypogammaglobulinemia."