MS-2471

A 45-year-old man presents to the emergency department with worsening shortness of breath. He reports experiencing these symptoms for the past three months, which worsen with physical activity or walking long distances. He has a history of multiple sexual partners and recalls having painless ulcer-like lesions on his genitals and a rash on his hands many years ago, but did not seek treatment due to lack of medical insurance. The patient denies chest pain and fever. A Doppler echocardiography reveals significant aortic root dilatation and aortic regurgitation. What is the most likely underlying pathology in this case?