Moreover, the levels of Munc18-2 and syntaxin-11 in patients with a homozygous missense mutation are markedly lower than those of patients with a homozygous splice-site mutation or with compound heterozygosity with a splice-site mutation.[6] Therefore, we suppose this patient did not develop HLH until 9 years of age due to the compound heterozygosity of STXBP2, which includes the splice-site mutation in exon 15. This evidence concerns the gene STXBP2 and hemophagocytic syndrome.