Although the survival results of different subgroups of f-HLH were not given in the HLH-1994 study [22], in the HLH-2024 study, 5-year OS values in children with PRF1, UNC13D, STX11 and STXBP2 mutations were 70%, 70%, 80% and 71%, respectively. This evidence concerns the gene PRF1 and hemophagocytic syndrome.