From the Guidelines
McArdle disease symptoms typically include exercise intolerance, muscle cramps, pain, and fatigue that occur during physical activity, as well as elevated creatine kinase levels in the blood, especially after exercise 1.
Key Symptoms
- Exercise intolerance
- Muscle cramps
- Pain
- Fatigue
- Elevated creatine kinase levels
- Rhabdomyolysis (muscle breakdown) with intense exercise
- Myoglobinuria (dark urine)
- Fixed muscle weakness in some patients as they age
Disease Characteristics
McArdle disease, also known as glycogen storage disease type V, is characterized by the body's inability to break down glycogen in muscles due to phosphorylase deficiency, forcing reliance on alternative energy pathways during exercise 1.
Diagnostic Considerations
The symptoms of McArdle disease can be distinguished from other glycogen storage diseases, such as Pompe disease and GSD III, by the presence of exercise-induced muscle cramps, significantly elevated CK levels, and the absence of hepatomegaly and hypoglycemia 1.
Management
Management of McArdle disease focuses on lifestyle modifications, including moderate aerobic exercise, proper warm-up periods, and avoiding intense anaerobic activities, as there is no specific medication to treat the condition 1.
From the Research
McArdle Disease Symptoms
- Exercise-induced pain
- Cramps
- Fatigue
- Myoglobinuria
- Acute renal failure 2, 3, 4
- Rhabdomyolysis 3, 4
- Exercise intolerance 2, 3, 4
- Failure to thrive 4
- Elevated creatine kinase levels 4, 5
- Increased serum lactate is not present following ischemic exercise 4
Diagnosis and Treatment
- Diagnosis is supported by laboratory tests showing myoglobinuria and elevated creatine kinase levels 4
- Genetic testing can confirm the presence of mutations in the PYGM gene 4
- Treatment includes a diet rich in slow-absorbing carbohydrates, regular low-intensity physical exercise, and supplementation with vitamin B6 and creatine 4, 5, 6
- Vitamin B6 supplementation may be beneficial for reducing fatigability and improving glycogenolysis 5, 6
Prognosis and Complications
- Prognosis is generally favorable with proper disease management 4
- Vigorous exercise should be avoided to prevent complications such as severe muscle injury and rhabdomyolysis 4
- McArdle disease is likely underdiagnosed and should be considered in the differential diagnosis of rhabdomyolysis in all patients with symptoms of exercise intolerance and/or recurrent myoglobinuria 4