5th February 2024

This is a 55-year-old gentleman with a history of fatiguability that worsened on exertion.

This is a 55-year-old gentleman with a history of fatiguability that worsened on exertion. This is alleviated after meals, and there were no diurnal symptom fluctuations. 

Blood tests revealed raised creatine kinase, lactate dehydrogenase and myoglobulin. A muscle biopsy specimen stained for glycogen showed subsarcolemmal accumulation of “lakes” of glycogen.

Which of the following is the most likely diagnosis?