Wiskott–Aldrich syndrome (WAS, OMIM #301000) is a rare and severe X-linked recessive primary immunodeficiency disease caused by WAS gene mutations, with an approximate incidence of 1/1,000,000 to 10/1,000,000.[1–5] Due to different WAS gene mutations, there are diverse clinical phenotypes, ranging from classic WAS to X-linked thrombocytopenia (XLT, OMIM #313900) and X-linked neutropenia (OMIM #300299). The gene discussed is WAS; the disease is Wiskott-Aldrich syndrome.