**3.19 Wiskott-Aldrich syndrome (WAS)**

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive primary immunodeficiency disease caused by mutations of the WAS protein (WASP) gene. The WASP gene is located on chromosome Xp11.22–Xp11.23. It has 12 exons, and encodes 502 amino acids. Patients with Wiskott-Aldrich syndrome have smaller platelets and lymphocytes, and their platelet counts are decreased; they have bleeding problems, recurrent bacterial and viral infections, and higher risk of autoimmune diseases and cancers. This disease affects about 1-10 in 1 million of live births (Aiuti & Roncarolo, 2009; Bouma et al., 2009; Dupré et al., 2004; Jin et al., 2004; Qasim et al., 2009; Ramesh et al., 1997; Zhu et al., 1997).
