A right-sided aortic arch and aberrant left subclavian artery with proximal segment hypoplasia.

The right-sided thoracic aortic arch is a rare congenital malformation occurring during embryologic development. A majority of the cases present with two anatomic variations, one of which is an aberrant left subclavian artery (LSA) originating off the distal descending aortic arch. This aberrant LSA courses across and compresses thoracic structures on its way to the left thoracic outlet. While this aberrant vessel causes mostly benign symptoms, patients may first present with rupture of a thoracic aneurysm. This thoracic aneurysm is commonly known as Kommerell's diverticulum. This paper presents a case of an aberrant LSA originating off Kommerell's diverticulum with a proximal long-segment hypoplasia, a very rare anatomic variation.