Histiocytoid cardiomyopathy with hypotonia in an infant.

A 15 month old female, who had suffered from ventricular tachycardia from the prenatal period, experienced cardiac arrest at home. Once she had recovered, ventricular tachycardia occurred repeatedly. She died 7 months after admission. At autopsy, the heart showed many yellowish white nodules in the endocardium. Histologically these nodules consisted of granular or foamy histiocyte-like cells, which had spread to all four chambers. Electron micrographs showed mitochondrial hyperplasia in these cells. The cells had some myofibrils in their cytoplasm. These findings were compatible with histiocytoid cardiomyopathy. Interestingly, the present case showed hypotonia. Her muscle biopsy revealed decreased activity of cytochrome c oxidase, suggesting that histiocytoid cardiomyopathy is related to mitochondrial cytopathy.