Large pericardial effusion requiring pericardiocentesis as cardinal sign of macrophage activation syndrome in systemic onset-juvenile idiopathic arthritis.

We report a case of large pericardial effusion which has been managed with pericardiocentesis as the main presentation feature of a dramatic clinical picture, only retrospectively framed as referred to macrophage activation syndrome in a child with juvenile idiopathic arthritis at its onset. The risk of developing this rare and severe complication should be recognized in various pathological settings of childhood, above all in children displaying systemic signs of juvenile idiopathic arthritis.