Ochronosis of Mitral Valve and Coronary Arteries.

Cardiac ochronosis is a rare complication of alkaptonuria, a disorder of tyrosine metabolism characterized by a triad of dark urine, pigmentation of tissues, and ochronotic arthropathies. When present, cardiac ochronosis generally affects the aortic valve, resulting in aortic stenosis. More rarely, it may affect the mitral valve and the coronary arteries.