Hence, XLP can be divided into two types: SAP deficiency (XLP1), caused by mutations in SH2D1A, and XIAP deficiency (XLP2), due to mutations in XIAP. Although SAP and XIAP deficiencies share some common clinical features, such as HLH and dysgammaglobulinemia, they also have their own specific manifestations. The gene discussed is XIAP; the disease is X-linked lymphoproliferative syndrome.