Mutation of Munc13-4 results in another form of familial hemophagocytic lymphohistiocytosis (FHL3) (Feldmann et al., 2003) and Munc13-4 deletion from murine platelets results in complete ablation of dense-granule release and impaired release from α-granules in vitro indicating its importance in Ca2+ regulation of SNARE interactions with the plasma membrane (Ren et al., 2010). Here, UNC13D is linked to Familial hemophagocytic lymphohistiocytosis.