Review Question - QID 214929

A 6-month-old boy is brought to clinic for shortness of breath. For the past 2 days, his parents have noticed increasing irritability and work of breathing. They report an uncomplicated pregnancy and delivery, but since the patient’s birth, he has had multiple episodes of thrush and was hospitalized 2 months prior with a viral pneumonia. His temperature is 101.2°F (38.4°C), blood pressure is 90/52 mmHg, pulse is 140/min, and respirations are 50/min. Physical exam is notable for low-set ears, a hypoplastic jaw, bilateral crackles, and a grade III/VI systolic murmur heard best at the left sternal border. The abnormal development of which of the following is associated with this patient’s condition?