WAS and immunodeficiency disease: Wiskott-Aldrich syndrome (WAS) is a rare X-linked genetic human disease associated with thrombocytopenia, eczema, and life-threatening immunodeficiency.1,2 Patients often also have an increased incidence of autoimmune disease and malignancies.3,4 WAS is caused by mutations in the gene encoding the Wiskott-Aldrich syndrome protein (WASP), which is a member of a family of proteins that are required for the transduction of signals from the cell surface to the actin cytoskeleton.5