Right-Left Differential Cyanosis in a Newborn With a Circumflex Retroesophageal Left Aortic Arch

BACKGROUND: Differential cyanosis typically results from right-to-left shunting through the patent ductus arteriosus (PDA), supplying highly oxygenated blood from the left ventricle to the upper body, whereas the lower body receives desaturated blood from the right ventricle. CASE SUMMARY: A term newborn presented with cyanosis of the right arm, right chest wall, and adjacent right-sided upper abdominal wall. Echocardiography and computed tomography revealed a circumflex retroesophageal left aortic arch with bilateral PDA, nonconfluent pulmonary arteries, and aberrant right subclavian artery that arose from the distal aortic arch, where the widely patent right-sided PDA originated with right-to-left shunting. Surgical repair with division of both PDA resulted in resolution of cyanosis. DISCUSSION: Territorial differential cyanosis can be seen between the right and left sides of the body when there is an aberrant origin of a subclavian or brachiocephalic artery from the descending aorta, combined with ipsilateral ductal right-to-left shunting. TAKE-HOME MESSAGE: While typically seen between the upper and lower body, differential cyanosis may also occur between right and left sides of the upper body.