X-linked lymphoproliferative syndrome. An immunodeficiency disorder with acquired agammaglobulinemia, fatal infectious mononucleosis, or malignant lymphoma.

The X-linked lymphoproliferative syndrome (XLP) is characterized by a combined variable immunodeficiency with vulnerability to Epstein-Barr virus (EBV)-induced fatal or chronic infectious mononucleosis, acquired agammaglobulinemia, aplastic anemia, or malignant B cell lymphomas. Diagnosis of XLP requires documentation of two or more maternally related males with these phenotypes. Epstein-Barr virus must be demonstrated in circulating blood, lymphoid tissues, or saliva of infected males. Characteristically, the patients have low-titer antibodies to EBV and often lack anti-EB nuclear-associated antibody due to T cell defects. Thymus gland is often depleted and epithelium may be destroyed. Thymic-dependent regions in lymph nodes and spleen are depleted and immunoblastic transformation with plasma cell differentiation is seen. The carrier females exhibit partial immune deficiency and have paradoxically elevated antibodies to EBV. Our registry of XLP provides consultation and comprehensive study of persons and families with the syndrome.