A 24-year-old male presents with different blood pressures in upper and lower extremities, with a late systolic murmur. What is the likely diagnosis?

The presentation of differing blood pressures in the upper and lower extremities, combined with a late systolic murmur, suggests coarctation of the aorta. In this condition, there is a narrowing of the aorta, typically just distal to the left subclavian artery. This anatomical change leads to higher blood pressures in the arms (upper body) compared to the legs (lower body) because of the increased resistance to blood flow beyond the coarctation.

The late systolic murmur that accompanies this condition is often due to collateral circulation that develops over time as the body compensates for the differential blood flow and pressures. These collaterals can create turbulent blood flow and lead to the characteristic murmur.

Other conditions, while they may present with specific murmurs or differential blood pressures, do not typically account for the same pattern observed in coarctation of the aorta. Hypertrophic obstructive cardiomyopathy is primarily associated with dynamic obstruction to outflow and characteristic heart sounds but does not cause a systemic difference in blood pressures between extremities. Patent foramen ovale and patent ductus arteriosus are congenital heart conditions that primarily affect shunting of blood rather than creating upper and lower body blood pressure discrepancies.