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.