The Wiskott-Aldrich syndrome (WAS) is a primary immunodeficiency determined by mutations in the WAS-protein (WASp), a member of a larger family of proteins (WASP family) that functions as nucleation-promoting factors for the Arp2/3 complex, which drives the generation of branched actin filaments (110). The gene discussed is WAS; the disease is Wiskott-Aldrich syndrome.