Macrophage activation syndrome(MAS) is a complication of bone marrow suppression, coagulopathy and CNS dysfunction which occurs in rheumatic diseases. Normally the (Hemophagocytic Lympho-Histiocytosis) HLH-2004 criteria is used to diagnose patients with MAS. However this criteria is probably not sensitive and would probably be fulfilled quite late into the disease. Thus there would be an unacceptable delay. Ravelli et al came up with a different set of criteria based on data of patients reported in literature.