[Delay in the diagnosis of McArdle's disease].

We describe the case of a 14-year-old patient with fatigability and muscular cramps beginning in the first infancy and started by physical exercise. The clinical record, the increase of creatinine-kinase without clinical or biological signs of inflammation and the electromyographic normality, suggested the presence of this disease, which was confirmed through microscopic studies (optic and electronic) and histochemistry. We review the clinical and biological characteristics, the diagnostic methods for this type of glycogenosis and its differential diagnosis, because we think that the low suspicion levels among the clinicians contribute to the few cases published in the literature.