Ventricular thrombosis in Sipple's syndrome.

An 18-year-old girl with multiple endocrine neoplasia type 2 (Sipple's syndrome) had a large intraventricular mass that proved to be a thrombus. She had no apparent precipitating factor for intracavitary thrombus formation. This is the first reported case of multiple endocrine neoplasia associated with ventricular thrombus. A hypercoagulable state resulting from catecholamine-induced and serotonin-induced platelet hyperaggregability might have been the causative mechanism.