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X-linked lymphoproliferative syndrome (Duncan syndrome): causes, symptoms, diagnosis, treatment
Medical expert of the article
Last reviewed: 07.07.2025
X-linked lymphoproliferative syndrome results from a defect in T-lymphocytes and natural killer cells and is characterized by an abnormal response to Epstein-Barr virus infections, leading to liver damage, immunodeficiency, lymphoma, fatal lymphoproliferative disease, or bone marrow aplasia.
X-linked lymphoproliferative syndrome is caused by a mutation in a gene on the X chromosome that codes for a protein specific to T lymphocytes and natural killer cells called SAP. Without SAP, lymphocytes proliferate uncontrollably in response to Epstein-Barr virus (EBV) infection, and natural killer cells do not function.
The syndrome is asymptomatic until exposure to EBV. Most patients then develop rapid or fatal mononucleosis with liver damage (caused by cytotoxic T cells that target EBV-infected B cells and other cellular elements); survivors of primary infection develop B-cell lymphomas, aplastic anemia, hypogammaglobulinemia (similar to CVID), or a combination of these.
The diagnosis in survivors of primary EBV infection is based on the presence of hypogammaglobulinemia, decreased antibody response to antigen (especially EBV nuclear antigen), impaired T-cell proliferation in response to mitogens, decreased natural killer function, and inversion of the CD4:CD8 ratio. Genetic diagnosis of the mutation is possible before EBV infection and development of symptoms.
Most patients survive no more than 10 years, the rest die before the age of 40, unless a bone marrow transplant is performed, which provides significant curative effect if performed before EBV infection.