Overview

• autosomal recessive type V glycogen storage disease
• caused by myophosphorylase deficiency
• this causes decreased muscle glycogenolysis

Features

• muscle pain and stiffness following exercise
• muscle cramps
• second wind phenomenon
  • occurs when patients experience an improvement in exercise tolerance after a brief rest or reduction in intensity
  • due to the body's switch from glycogen-dependent energy metabolism to increased reliance on circulating glucose and fatty acids
  • his adaptation allows for better energy utilisation during prolonged activity despite the underlying myophosphorylase deficiency.
• rhabdomyolysis & myoglobinuria
• low lactate levels during exercise