XIAP and piebaldism: In addition to the patients with FHL and partial albinism (defined on the basis of the partial or complete absence of normal hair color), 45 additional patients with suspected FHL (caused by either familial disease or a confirmed severe functional defect in degranulation or cytotoxicity assays) and apparently normal pigmentation were identified, in whom we did not find biallelic mutations in the FHL-related genes PRF1, UNC13D, STX11, and STXBP2 (or SH2D1A for XLP1 and XIAP for XLP2 in male subjects).