27th June 2023

A 45-year-old man presents with gradually worsening shortness of breath on exertion and difficulty in running

A 45-year-old man presents with gradually worsening shortness of breath on exertion and difficulty in running. On examination, he has bilateral ptosis, and you notice he is slow to let go of his coffee mug after placing it down. ECG shows a prolonged PR interval, right bundle branch block, and echocardiogram reveals an ejection fraction of 35%. Family history is significant for his brother has a muscle condition and his nephew died in infancy.

Select the SINGLE most likely diagnosis from the list below. Select ONE option only.