Large deletion of the X-linked lymphoproliferative disease gene detected by fluorescence in situ hybridization

The X-linked lymphoproliferative disease (XLP) is an inherited immunodefici ency characterized by an abnormal responses to infection with Epstein-Barr virus (EBV), resulting in fatal infectious mononucleosis, hypogammaglobulin emia, virus-associated hemophagocytic syndrome, and malignant lymphoma. Mut ations in the gene coding for a T cell-specific SLAM-associated protein (SA P) have been recently identified in XLP patients. We report on a 1-year-old boy representing fulminant hemophagocytic syndrome. He developed high feve r, lymphadenopathy, hepatosplenomegaly with liver dysfunction, and pancytop enia with marrow hemophagocytosis, EBV DNA was abnormally increased in the blood. Polymerase chain reaction failed to amplify SAP mRNA and genomic DNA products from the patient's peripheral blood. A large deletion of the SAP gene was confirmed by fluorescence in situ hybridization (FISH), FISH analy sis also disclosed that the patient's mother was a carrier. We conclude tha t FISH can be useful in the diagnosis of XLP with large deletions of the SA P gene and its carrier state. Am. J, Hematol, 64: 128-132, 2000, (C) 2000 W iley-Liss. Inc.