Importance:Acute necrotizing encephalopathy(ANE)is a rare disease with high mortality.Plasma exchange(PLEX)has recently been reported to treat ANE of childhood(ANEC),but its efficacy is uncertain.Objective:This study aimed to investigate the effectiveness of PLEX on ANEC.Methods:A retrospective study was conducted in four pediatric intensive care units from December 2014 to December 2020.All patients who were diagnosed with ANEC were included;however,these patients were excluded if their length of stay was less than 24 h.Participants were classified into PLEX and non-PLEX groups.Results:Twenty-nine patients with ANEC were identified,10 in the PLEX group and 19 in the non-PLEX group.In the PLEX group,C-reactive protein,procalcitonin,alanine aminotransferase,and aspartate aminotransaminase levels were significantly lower after 3 days of treatment than before treatment(13.1 vs.8.0,P=0.043;9.8 vs.1.5,P=0.028;133.4 vs.31.9,P=0.028;282.4 vs.50.5,P=0.046,respectively).Nine patients(31.0%,9/29)died at discharge,and a significantly difference was found between the PLEX group and non-PLEX group[0 vs.47.4%(9/19),P=0.011].The median follow-up period was 27 months,and three patients were lost to follow-up.Thirteen patients(50.0%,13/26)died at the last follow-up,comprising three(33.3%,3/9)in the PLEX group and ten(58.8%,10/17)in the non-PLEX group,but there was no significant difference between the two groups(P=0.411).Three patients(10.3%,3/29)fully recovered.Interpretation:PLEX may reduce serum C-reactive protein and procalcitonin levels and improve liver function in the short term.PLEX may improve the prognosis of ANEC,and further studies are needed.