26th April 2024

A 10-year-old girl presents with a six-month history of progressive fatigue and exercise intolerance.

A 10-year-old girl presents with a six-month history of progressive fatigue and exercise intolerance. She also reports occasional palpitations and shortness of breath, especially when playing sports. There is no history of fever, chest pain, or syncope. On examination, there is a faint cyanosis of the lips and nail beds. A heart murmur is heard on auscultation, loudest at the left lower sternal border, with a diastolic component.

Which is the most likely diagnosis?