LYST and hemophagocytic syndrome: Defective degranulation is classically described in patients with familial HLH (FHL) due to a genetic defect in one of the three genes; UNC13D, STX11, STXBP2 and in HLH patients with hypopigmentation resulting from a genetic defect in LYST, RAB27a, AP3B1, and AP3D1 genes (19).