UNC13D and hemophagocytic syndrome: Genetic mutations associated with HLH—such as those in familial HLH (PRF1, UNC13D, and STX11 genes), several granule/pigment-abnormality genes (RAB27A, LYST, AP3B1), X-linked lymphoproliferative disease genes (SH2D1A, XIAP), and others such as nlrc4 and cdc42—can significantly influence an individual’s susceptibility to developing HLH in response to viral infections.