[McArdle's disease with insulin resistance caused by obesity].

We reported a 29-year-old woman with McArdle's disease accompanied with insulin resistance. The patient was referred to our hospital because of muscle tenderness, swelling and weakness of lower extremities, and elevated serum CK level. Ischemic forearm exercise test showed no elevation in serum lactate and pyruvate levels. Muscle biopsy revealed significant reduction in phosphorylase activity both histochemically and biochemically. Pre-administration of glucagon had no effect on serum lactate and pyruvate levels after ischemic forearm exercise test while serum glucose elevated. The glucose clamp test confirmed insulin resistance. There was no reduction in number of insulin receptor or activity of tyrosine kinase. Her bodyweight was 78.4 kg and body mass index (BMI) was high as 32.0. Her obesity might be a causative factor of insulin resistance.