Background Macrophage activation syndrome (MAS) is a severe,potentially life-threatening syndrome.Here we aim to review the precipitating events,clinical features,treatment,and outcome of macrophage activation syndrome (MAS).Part patients were analysed the Polymorphisms of Perforin A91V (NCBI:SNP rs35947132) using special primers by polymerase chain reaction (PCR).Methods Retrospective review of cases of MAS from a prospectively collected database of children with autoimmune diseases from 2003 to 2008.