Fibromuscular dysplasia is a common vascular disease, which mainly affects the renal arteries. In this study, we report the case of a 1-day-old infant who presented with severe left ventricular dysfunction immediately after birth, and subsequently died 3 days postnatally. At autopsy, an extensive myocardial infarction of the left ventricle and the septum was found, caused by an isolated fibromuscular dysplasia of left coronary artery.