Mutations in the WAS gene have been associated with three clinical presentations: Wiskott-Aldrich syndrome and X-linked thrombocytopenia, which are associated with loss-of-function mutations, and X-linked neutropenia, which is associated with activating mutations. Wiskott-Aldrich syndrome, the most severe presentation, is classically characterized by thrombocytopenia (with small platelet size), eczema, increased susceptibility to pyogenic and opportunistic infections, and increased risk of autoimmune disease and cancer, specifically lymphomas. If untreated, this syndrome typically leads to death in early childhood or adolescence. Individuals with X-linked thrombocytopenia have thrombocytopenia (which can present intermittently), and mild or no eczema or immune deficiency. Though individuals with XLT typically have a normal lifespan, they are still at increased risk for severe disease-related complications. Individuals with XLN have a persistent neutropenia due to a promyelocyte/myelocytic maturation arrest and recurrent bacterial infections.