When we compared the levels of the cytokines between the primary and secondary HLH groups, the IL-4 level in primary-HLH was significantly lower than that in secondary HLH (P = 0.025), with the gap of IL-4 between the two groups was 1.6–1.9 pg/ml, and IFN-γ level in primary HLH had a tendency of statistically lower than that in secondary HLH (P = 0.051), with the gap of IFN-γ between the two groups was 393.9–530.7 pg/ml. This evidence concerns the gene IFNG and hemophagocytic syndrome.