Review Question - QID 108565

A 30-year-old man is brought into the emergency room for complaints of acute onset chest pain and shortness of breath. He has a history of intellectual disability and lives at home with his adoptive parents. His parents say that he has not seen a doctor since he was adopted as child and that he currently takes no medications. The patient’s temperature is 99.1°F (37.3°C), pulse is 108/min, blood pressure is 125/70 mmHg, respirations are 25/min, and oxygen saturation is 92% on 2L nasal canula. Physical exam is notable for a tall, thin individual with high-arched feet and mild pectus excavatum. There is mild asymmetry in the lower extremities with discomfort to dorsiflexion of the more swollen left leg. Lung auscultation reveals no abnormalities. What is the next step in the diagnosis of this patient’s underlying disorder?