A 26-year-old woman collapsed and died suddenly while dancing. Autopsy findings included the cutaneous lesions of pseudoxanthoma elasticum (PXE), a rare genetic disease with autosomal dominant and recessive inheritance patterns. Pathologic findings of PXE (degenerated elastic fibers) were seen in the stenotic epicardial coronary arteries, the intramyocardial arterioles, the subendocardium, the mitral valve, and the blood vessels of other viscera. The mitral valve was slightly myxoid. Intramyocardial arteriolar involvement has not been previously described in PXE. The other cardiac findings have only been described in a few cases. Although mitral valve prolapse in PXE has been shown echocardiographically, it is unclear whether or not the mitral valve findings in this case represent the substrate for this condition. It is important that autopsy pathologists search carefully for the pathognomonic skin lesions of PXE in cases of sudden death associated with coronary disease, mitral valve prolapse, or endocardial lesions. Recognition of this disease is essential for proper genetic counseling of surviving family members.