From the Research
McArdle disease is a rare genetic disorder that affects how the body processes glycogen, a form of stored energy in muscles, and the most effective management approach includes moderate aerobic exercise, avoiding intense exercise, and consuming simple carbohydrates before planned activities, as supported by the most recent study 1.
Definition and Cause
McArdle disease, also known as glycogen storage disease type V, is caused by a deficiency of the enzyme myophosphorylase, which prevents muscles from breaking down glycogen into glucose for energy during exercise. This deficiency leads to impaired glycogen breakdown in skeletal muscle, resulting in exercise intolerance, muscle cramps, and episodic weakness.
Symptoms and Diagnosis
People with McArdle disease typically experience muscle pain, cramping, and fatigue during physical activity, especially during the first few minutes of exercise. They may also develop muscle weakness and experience a "second wind" phenomenon where symptoms temporarily improve after initial discomfort. Diagnosis is often delayed or misattributed to other neuromuscular disorders, but can be confirmed through whole-exome sequencing, which identifies pathogenic variants in the PYGM gene, as seen in a recent case study 1.
Management and Treatment
There is no cure for McArdle disease, but management includes:
- Moderate aerobic exercise with appropriate warm-up periods
- Avoiding intense exercise
- Maintaining good nutrition
- Consuming simple carbohydrates before planned activities Some patients may also benefit from consuming glucose or other simple sugars before exercise to provide an alternative energy source for their muscles, as suggested by earlier studies 2, 3.
Recent Developments
A recent study 4 developed a Continuum of Care model for McArdle disease, which outlines five pivotal steps to streamline assessments and assist clinicians in determining patient-specific learning needs. This model serves as a translational tool to help optimize care for patients with McArdle disease. Another recent case study 1 highlights the importance of considering McArdle disease in children presenting with recurrent exertional muscle weakness and myalgias, and demonstrates the effectiveness of a structured nutritional and exercise regimen in improving symptoms.