STXBP2 and Epstein-Barr virus infection: One of them was a 5-year-old male with recurrent HLH secondary to EBV infection, who had two variants in one STXBP2 allele, (NM_001272034.1:c.[828-4C > T;1502G > A], p.(?;Arg501Gln)], both inherited from the father.