Macrophage Activation Syndrome Presenting with Pericardial Effusion, Hyponatremia and Renal Involvement.

Background: Macrophage activation syndrome is a rare and life threatening complication of childhood rheumatic disorders. Case characteristics: 6-year-old male child with macrophage activation syndrome complicating systemic onset juvenile idiopathic arthritis. Observation: He developed pericardial effusion, hyponatremia and deranged renal function. Outcome: Improvement on intravenous cortico steroids. Message: High index of suspicion can lead to earlier diagnosis of macrophage activation syndrome.