Clinical symptoms of acute or chronic myocardial ischemia due to congenital coronary anomalies occasionally develop during adult life. While several types of coronary anomalies have been already reported, origin of the coronary arteries outside of the ascending aorta and pulmonary trunk is exceedingly rare, and has indeed been described to date only in a 6-day-old newborn. We hereby report to the best of our knowledge the first and unique case of an adult patient with ischemic cardiomyopathy, in whom coronary angiography and aortography disclosed both left main trunk hypoplasia and subsidiary left coronary supply provided by an ectopic artery arising from the descending thoracic aorta.