[McArdle's disease without typical symptoms].

A 25-year-old female with McArdle's disease was reported. She had no characteristic symptoms for McArdle's disease such as muscle cramp and brown urine, but had general fatiguability from childhood. On examination, she showed no neurological abnormalities including muscle atrophy and weakness. On laboratory examination, serum creatinine kinase (CK) level was elevated, though serum lactic acid level remained unchanged after the ischemic forearm exercise test. Muscle biopsy from the biceps brachii showed almost completely absent phosphorylase activity both histochemically and biochemically. Thus, she was diagnosed as having McArdle's disease. The skinned fiber test of the muscle showed no enhanced Ca induced Ca release (CICR), and serum VLDL level was normal. Her 27-year-old elder brother had similar clinical symptoms and serological abnormalities and may also have McArdle's disease, although muscle biopsy was not performed. A possibility of McArdle's disease should be considered when we encounter a patient who has only general fatigue and high serum CK level.