The first genes that is responsible for XLP was identified as the SH2D1A/SLAM-associated protein (SAP) gene in 1998 [4-6], and mutations in the X-linked inhibitor of apoptosis protein (XIAP) gene can also lead to the clinical phenotype of XLP in 2006 [7]. The gene discussed is SH2D1A; the disease is X-linked lymphoproliferative disease.