Unusual dominant course of left circumflex coronary artery to right coronary artery territory with absent right coronary artery.

A single coronary artery (SCA) is a rare congenital anomaly of the coronary circulation, which is often associated with other congenital anomalies. The reported incidence of a SCA ranges from 0.6 to 1.3% of the population undergoing coronary angiography. The absence of the right coronary artery (RCA) with the origin of the RCA arising from the distal circumflex artery is an extremely rare variant of the SCA. The incidence of the anomaly is uncertain, with few cases reported. We report the case of a 68-year-old female, in whom the RCA arises as an extension of the distal left circumflex coronary artery.