A metabolic muscle disease.

A 61-year-old woman presented with a life long history of fatigability which worsened on exertion. She became fearful of exercising and thus was labelled as "lazy" by family and friends. After being started on simvastatin she was found to have raised creatine kinase (CK) values, which remained elevated despite stopping the drug. On the basis of the history, McArdle disease was suspected and a muscle biopsy confirmed it.