Objectives Macrophage activation syndrome (MAS) is a severe, potentially life-threatening syndrome.Here we aim to review the precipitating events,clinical features, treatment, outcome and perforin A91V gene analysis in systemic onset juvenile idiopathic arthritis (SoJIA) children with MAS.

Methods Retrospective review of cases of MAS from a collected database of fourteen children with SoJIA from 2003 to 2008. Gene-specific polymerase chain reaction (PCR) primers were used to analyze the perforin A91V gene polymorphism.

Results Fourteen patients (nine boys) were considered to have evidence of MAS, with age ranged from 4 months to 12 years.The primary diagnosis was systemic onset juvenile idiopathic arthritis.No medication was identified as trigger. Eleven had infections prior to MAS,specific infectious agents were identified in four. High fever, new onset hepatosplenomegaly, lymphadenopathy, liver dysfunction,abnormal lipid metabolism and hemophagocytosis were common clinical features.Two cases were with acute respiratory distress syndrome (ARDS),multiple organ failure (MOF) in three and three died. The perforin A91V (NCBI:SNP rs35947132) variant gene was detected in seven systemic onset juvenile idiopathic arthritis compolicated with MAS cases, but no mutation were found. Glucocorticoid, intravenous immunoglobulin, immunoimpressive therapy were effective and HP (Plasmapheresis) used in one serious case was also effective.

Conclusions MAS is a rare and potentially fatal complication of childhood rheumatoid diseases,especially systemic onset juvenile idiopathic arthritis. Most of our patients were male, and most cases were preceded by infection. Bone marrow studies support the diagnosis. MOF may be a poor prognostic sign.Aggressive early therapy is essential.

Disclosure of Interest None declared