Since then, the study of familial cases allowed the recognition of genetic alterations directly affecting proteins involved in cytotoxic activity, such as Munc13-4 (FHL-3), Syntaxin 11 (FHL-4), Munc18-2 (FHL-5), RAB27A (Griscelli Syndrome type 2, GS2), LYST (Chediak-Higashi Syndrome, CHS) (11–15). This evidence concerns the gene UNC13D and Griscelli disease type 2.