McArdle disease: a case report and review

Alberto Leite, Narciso Oliveira, Manuela RochaInternal Medicine Department, Hospital de Braga, PortugalAbstract: McArdle disease (glycogen storage disease type V) is a pure myopathy caused by an inherited deficit of myophosphorylase. The disease exhibits clinical heterogeneity, but patients typically experience exercise intolerance, acute crises of early fatigue, and contractures, sometimes with rhabdomyolysis and myoglobinuria, triggered by static muscle contractions or dynamic exercise. We present the case of a 54-year-old man with a lifelong history of fatigability, worsening on exertion. Laboratory evaluation revealed significant elevations in levels of creatine kinase (7924 U/L), lactate dehydrogenase (624 U/L), and myoglobulin (671 ng/mL). A muscle biopsy confirmed the presence of McArdle disease. This case report illustrates how, due to embarrassment, the patient hid his symptoms for many years and was eventually extremely relieved and “liberated” once McArdle disease was diagnosed 40 years later.Keywords: McArdle disease, glycogen storage disease, myophosphorylase