**2. Embryology**

Arteria lusoria results from abnormal embryologic development of the aortic arch. In the normal situation, between the 4th and 5th weeks of embryonic life, blood leaves the heart by a common trunk called the "truncus arteriosus", which divides into two branches termed the ventral aortae. These branches are connected with the paired dorsal aortae by six aortic arches. The carotid system is formed by segments of the first three arches. The right fourth arch, a segment of the right ventral aorta, and a portion of the right dorsal aorta develop into the right subclavian artery. The left fourth arch persists as the adult aortic arch with the anlagen of the seventh dorsal intersegmental artery, and this forms the left subclavian artery. The fifth arches are both resorbed, and the sixth arches form the pulmonary artery and the ductus arteriosus [5, 6].

The aberrant origin of the right subclavian artery is caused by the involution of the right fourth vascular arch and proximal right dorsal aorta and the persistence of the seventh intersegmental artery originating from the proximal descending thoracic aorta, resulting in the arteria lusoria following an abnormal course [5, 6].
