McArdle’s disease is a metabolic myopathy that manifests with varied clinical conditions and is often confounded with other diagnoses. Herein, the authors report a case series and carry out a literature review.
A cross-sectional single-center study evaluating 12 patients with McArdle’s disease was conducted.
Mean age at onset of symptoms was 28.0±17.4 years, while age at disease diagnosis was 39.0±14.8 years. History of intolerance to physical exercises was observed in 10 cases; muscle weakness in 9, second wind phenomenon in only 1 case. The presence of cramps, fatigue and myalgia was observed in 12, 11 and 9 of the cases respectively. Median creatine phosphokinase level was 5951U/L. Most of the patients (83.3%) were initially diagnosed with another condition (polymyositis, inclusion body myositis, fibromyalgia and/or muscular dystrophy), and approximately half had received glucocorticoids and/or immunosuppressants prior to definitive diagnosis. All patients underwent muscular biopsy, which revealed the presence of subsarcolemmal vacuoles characterized by glycogen deposits, and negative histochemical reaction for the myophosphorylase enzyme.
The present study reinforces the presence of clinical variability among patients and shows that McArdle’s disease should be considered one of the differential diagnoses of inflammatory myopathies and other rheumatic diseases.
Fibromyalgia; glycogen storage disease; myopathies; myophosphorylase; myositis