Focal giant-cell cardiomyopathy.

A newborn with supraventricular arrhythmia diagnosed during fetal life was found at autopsy to have a small nodule with hypertrophic and multinucleated myocardial cells in the atrial septum, near the atrioventricular node. There were no stigmata of Beckwith-Wiedemann syndrome or tuberous sclerosis. This focal giant-cell cardiomyopathy has been described only once, in an infant with Beckwith-Wiedemann syndrome. It is suggested that these dysplastic myocardial cells may be responsible for the atrial arrhythmia and that this hamartomatous lesion has the potential for malignant transformation.