Erdheim-Chester Disease: An Unusual Etiology of Recurrent Massive Pericardial Effusion.

Erdheim-Chester disease (ECD), a rare non-Langerhans cell histiocytosis, involves multiple systems and may display pericardial effusion. Herein, we report a 60-year-old man who presented with refractory pericardial effusion of "unknown" etiology. As in this patient, ECD should be considered when rapidly recurrent pericardial effusion is accompanied by a pseudotumoral lesion of the right atrium and other systemic manifestations.