X-linked lymphoproliferative disease

X-linked lymphoproliferative disease, also known as Duncan disease or Purtilo syndrome and abbreviated XLP, is a lymphoproliferative disorder usually caused by mutations in the SH2D1A gene in males. People with the disorder have immune system deficiencies that leave them unable to respond effectively to the Epstein-Barr virus, a common virus that typically causes mild symptoms or infectious mononucleosis. Two variants are currently known, XLP1 and XLP2. XLP1 is estimated to occur in about one in every million males, while XLP2 is rarer, at about one in every five million males. Because of therapies such as chemotherapy and stem cell transplants, the survival rate of XLP1 has increased dramatically since the disease was first recognized in the 1970s.