PRF1 and lymphoproliferative syndrome: Nearly 58% FHL cases are reported to harbour mutations in PRF1 gene (located at 10q22.1) that alters the normal function of perforin [8]; whereas 40–60% of all X-linked lymphoproliferative disorders harbour mutation in SLAM-associated protein (SAP) regulating gene SH2D1A (located at Xq25) [9].