Coarctation of the aorta is a rare inherited birth defect where the heart blood vessel called the aorta has a narrowed area which affects blood flow. The degree of constriction is variable which mild cases asymptomatic until adulthood. The poor blood flow to the lower body gives results in it appearing less developed than that upper body. The atypical form of the condition involves the abdominal aorta, the ascending aorta or the descending thoracic aorta. The disease may be a congenital anomaly, caused by arteritis or associated with conditions such as Williams syndrome and neurofibromatosis. See also Atypical coarctation of aorta