Abstract: Objective? To?explore?the?comparison?of?the?clinical?features?between?Kawasaki?disease?(KD)?and?systematiconset?juvenile?idiopathic?arthritis?(SJIA)?with?macrophage?activation?syndrome?(MAS).?Method The clinical data of 5 cases of KD-MAS?and?8?cases?of?SJIA-MAS?children?admitted?from?September?2015?to?September?2019?were?retrospectively?analyzed.? Results? The?children?with?KD-MAS?were?all?male,?aged?from?5?months?to?7?years?and?10?months.?In?the?SJIA-MAS?group,?8? children?(3?boys?and?5?girls)?aged?from?1?year?and?2?months?to?11?years?had?10?times?of?MAS?in?total,?among?whom,?one?boy? and?one?girl?had?two?times?of?MAS?respectively,?and?the?age?at?recurrence?was?6?years?and?7?months,?and?8?years?and?5?months,? respectively.?The?main?clinical?manifestations?of?all?the?children?were?persistent?high?fever.?Comparison?of?laboratory?indicators? showed?that?ferritin?level?was?correlated?with?LDH?level?(r=0.071,?P=0.03).?The?median?ferritin?was?14900?ng/mL?and?the? median?LDH?was?1264.5?U/L?in?the?SJIA-MAS?group.?The?median?ferritin?and?LDH?in?the?KD-MAS?group?was?736?ng/ml?and? 492?U/L?respectively,?and?the?differences?between?the?two?groups?were?statistically?significant?(both?P<0.05).?One?case?in?the? KD-MAS?group?and?3?cases?in?the?SJIA-MAS?group?underwent?genetic?testing,?and?no?HLH-related?genes?were?detected.?The? condition?of?all?children?were?able?to?be?effectively?controlled.?Conclusion? LDH?may?serve?as?another?sensitive?indicator?for? early?identification?of?MAS?in?addition?to?ferritin.?There?are?differences?between?KD-MAS?and?SJIA-MAS?in?ferritin?and?LDH? levels.?The?application?of?SJIA-MAS?2016?diagnostic?criteria?to?diagnose?KD-MAS?is?more?sensitive.?KD-MAS?can?achieve? better?curative?effect?through?glucocorticoid?treatment,?and?the?prognosis?is?better?than?SJIA-MAS.

Key words: macrophage?activation?syndrome;? Kawasaki?disease;? systematic-onset?juvenile?idiopathic?arthritis;? ferritin; lactate dehydrogenase