Occult macrophage activation syndrome in systemic-onset juvenile idiopathic arthritic syndrome--a case report.

Macrophage activation syndrome (MAS) is a severe and life-threatening complication of rheumatic disorders in children. We described a 9-year-old girl in whom MAS developed as a complication of systemic juvenile idiopathic arthritis (S-JIA) at onset with obvious hemophagocytosis presented in the marrow. She suffered from high fever and generalized rash subsequently joints swelling for two weeks before admission. Physical examination revealed mild cervical lymphadenopathy and hepatosplenomegaly. Laboratory findings were: abnormal liver enzymes, increased triglyceride and ferritin levels, anemia .Hyperplasia of hemophagocytic macrophages was remarkable in her bone marrow. Methylprednisolone and cyclosporin therapy resulted in clinical and laboratory improvement. It is unusual that hemophagocytosis presented in the marrow at onset of So-JIA without obvious abnormal coagulation profile, thrombocytopenia and leucopenia. It seemed that MAS may be occult at onset of SJIA. It may be integral to the pathogenesis of SJIA. The proper cyclosporine serum lever at the onset of MAS is as high as 200-300 ng/ml.