XIAP and X-linked lymphoproliferative disease: Approximately 40–60% of XLP cases, classified as XLP type 1 (XLP1), are caused by germline mutations in SH2D1A, whereas a second type of the disease, in which patients harbor mutations in BIRC4, is categorized as XLP type 2 (XLP2); in the latter, patients present with recurrent splenomegaly, chronic colitis, and typical XLP phenotypes (Pachlopnik Schmid et al., 2011).