glycogen storage disease type-V (McArdle type glycogen storage disease)

Genetics

• associated with defects in PYGM

Clinical manifestations

• pain & stiffness after exertion
• exercise intolerance, muscle cramps, muscle weakness
• carbohydrate-rich diet improves exercise tolerance
• '2nd wind' phenomenon: a brief break after onset of symptoms allows for improved exercise tolerance

Laboratory

• myoglobinuria in 50%
• renal insufficiency
• PYGM gene mutation

Diagnostic procedures

• normal response of plasma glucose to IM glucagon

More general terms

• glycogen storage disease (glycogenosis)
• metabolic myopathy

Additional terms

• phosphorylase-M (myophosphorylase, muscle glycogen phosphorylase, PYGM)

Database

• OMIM: https://mirror.omim.org/entry/232600