Favorable outcome in patients with renal involvement complicating macrophage activation syndrome in systemic onset juvenile rheumatoid arthritis.

Systemic-onset juvenile rheumatoid arthritis (SoJRA) constitutes about 10-20% of all JRA. However more than two-thirds of the mortality seen in JRA patients is accounted for by SoJRA. Macrophage activation syndrome (MAS), which can also be considered as a form of secondary hemophagocytic lymphohistiocytosis, is a major cause of morbidity and mortality in children with SoJRA. MAS is characterized by persistent high fever, pancytopenia, mild to serious derangements of liver cell function, encephalopathy, and disseminated intravascular coagulation. Renal involvement in MAS is a rarely recognized feature. In 2 recently reported case series of MAS in SoJRA, renal involvement appeared to be associated with poor prognosis. We describe 3 children with SoJRA who had renal involvement complicating MAS and had a favorable outcome.