McArdle's Disease Diagnosed Following Statin-Induced Myositis

Ann Clin Biochem. 2004 Jul;41(Pt 4):338-40. doi: 10.1258/0004563041201554.


We describe the case of a 69-year-old man with a history of muscular symptoms dating back to his childhood; McArdle's disease (glycogen-storage disease V) was diagnosed following an episode of myositis in which a statin and physical exertion appear to have been precipitating factors. This case demonstrates that the ischaemic lactate-ammonia test still has a place in screening patients with symptoms suggestive of McArdle's disease and emphasizes the importance of carrying out glycogen phosphorylase histochemistry on the skeletal muscle biopsy to confirm the diagnosis. In patients who develop a raised plasma creatine kinase level or muscular symptoms during lipid-lowering therapy, the clinician should be alert to the possibility of an underlying myopathy.

Publication types

  • Case Reports

MeSH terms

  • Aged
  • Ammonia / blood
  • Anticholesteremic Agents / adverse effects
  • Creatine Kinase / blood
  • Glycogen Storage Disease Type V / diagnosis*
  • Glycogen Storage Disease Type V / metabolism
  • Humans
  • Lactic Acid / blood
  • Male
  • Muscle, Skeletal / metabolism
  • Myositis / chemically induced*
  • Myositis / metabolism
  • Physical Exertion
  • Simvastatin / adverse effects*


  • Anticholesteremic Agents
  • Lactic Acid
  • Ammonia
  • Simvastatin
  • Creatine Kinase