Mitral annular calcification (MAC) is a generally asymptomatic abnormality found commonly in aged hearts. Some clinical studies have suggested that MAC should be considered an independent risk factor for stroke; however, whether the abnormality is indeed a risk factor remains controversial. We report a case in which debris from a vulnerable caseous MAC contributed to lethal embolisms in multiple organs. Postmortem examination revealed that caseous materials originating from a collapsed MAC were trapped in stenosed atherosclerotic cerebral and coronary arteries. Our findings support the notion at that subtle debris from collapsed vulnerable MACs can trigger major and even lethal embolic events in patients with severe atherosclerotic stenosis in vital organs.