PRF1 and hemophagocytic syndrome: According to the 2018 HLH China Expert Consensus [6], 1094 patients underwent genetic testing, of which 128 patients tested positive for HLH-related mutations, with the following mutation frequencies for each gene: PRF1 23.4% (30/128), UNC13D 25.0% (32/128), LYST 14.0% (18/128), XIAP 12.5% (16/128), STXBP2 10.9% (14/128), STX11 5.5% (7/128), SH2DIA 5.5% (7/128), RAB27A 0.8% (1/128), BIRC4 0.8% (1/128), ITK 0.8% (1/128), MAGT 0.8% (1/128).