Oncocytic cardiomyopathy: a rare cause of unexpected early childhood death associated with fitting.

A 15-month-old girl died unexpectedly in hospital following a five-day history of intermittent cardiac arrhythmias and convulsions preceded by several weeks of occasional vomiting. Autopsy revealed subendocardial nodules in the left ventricle, and tricuspid and mitral valves that were composed of aggregated large cells with foamy, pale pink cytoplasm characteristic of oncocytic cardiomyopathy. Fat stains were positive for neutral lipid and phospholipid and electron microscopic examination revealed numerous irregular mitochondria within affected cells. Examination of the brain revealed no structural or histologic abnormalities, anoxic damage or thromboembolic material. Oncocytic cardiomyopathy, though rare, may cause unexpected death in previously well young children with quite variable preceding clinical symptoms and signs which include fitting. Although the aetiology is unknown there is evidence that mitochondrial dysfunction may be involved.