To date, five mutations in genes coding for proteins involved in cytotoxicity of lymphocytes, namely perforin (causing FHL2), Munc13–4 (FHL3), syntaxin-11 (FHL4) [5], and STXBP2 (FHL5) [6] have been found to cause FHL. The gene discussed is STX11; the disease is hemophagocytic syndrome.