UNC13D and hemophagocytic syndrome: Here, we present a 29-year-old male patient with Epstein–Barr virus (EBV)-triggered adult-onset HLH, who was found to carry compound heterozygous variants in the UNC13D gene (c.2588G>A and c.1978_1979insATTACCG) with complete T/NK cytotoxicity dysfunction.