An 8-month-old girl with Turner syndrome is brought to the emergency room by her parents, who complain that their daughter is breathing rapidly and not eating. Physical examination reveals tachypnea, pallor, absent femoral pulses, and a murmur heard at the left axilla. There is hypertension in the upper extremities and low blood pressure in both legs. A chest X-ray shows notching or scalloping of the ribs. What is the appropriate diagnosis?

Aortic coarctation is common, accounting for 6% of all cases of congenital heart disease. Coarctation usually occurs in the thoracic portion of the descending aorta, distal to the takeoff of the left subclavian artery at the site of the ductus arteriosus. The incidence of a bicuspid aortic valve in association with coarctation is 80% to -85%. The cardinal physical finding is diminution or absence of femoral pulses and hypertension in the upper extremities. Notching or scalloping of the ribs caused by marked enlargement of the intercostal collaterals can be seen on X-ray. None of the other choices exhibit these characteristics. Aortic valve stenosis (choice A) does not present with hypertension in the upper extremities.Diagnosis: Coarctation of aorta