Cytoskeleton and elastin disorders Quiz: Ace Your Exams

A 15-year-old boy comes to the office with his parent because of blurry vision, which has been ongoing for the past several months. The patient has had increasing difficulty seeing the board from the back of the classroom at school. He is otherwise healthy and enjoys playing basketball. Past medical history is significant for scoliosis, for which he wears a back brace and regularly follows-up with an orthopedic surgeon. Family history is significant for a history of aortic valve replacement in the patient’s father last year. Vitals are within normal limits. Slit-lamp examination shows bilateral upward lens subluxation. Physical examination reveals a patient at the 95th percentile for height and 50th percentile for weight, with long arms and legs, thin fingers, and a prominent, protruding sternum. A diastolic murmur is auscultated over the right upper sternal border. This patient most likely has an inherited defect in the gene encoding for which of the following proteins?