[X-linked lymphoproliferative syndrome (XLP syndrome): from clinic to gene]

X-linked lymphoproliferative syndrome (XLP, also known as Duncan's disease) is characterised by an extreme sensitivity to Epstein Barr virus (EBV), resulting in a complex phenotype manifested by severe or fatal mononucleosis, acquired hyogammaglobulinemia and malignant lymphoma. The gene responsible for XLP has recently been identified by a positional cloning and a functional cloning approach and encodes a small cytoplasmic protein involved in signal transduction of T and NK cells. The identification of the XLP gene will permit direct diagnosis of XLP in families with a single affected male. Recent progress in immunobiology and genetics of this primary immunodeficiency disease are presented.