McArdle’s Disease Questions and Answers
What is McArdle’s disease?
McArdle’s disease is a metabolic disease of skeletal muscle. Humans need the enzyme muscle phosphorylase to convert glycogen to glucose within cells during physical activity. In McArdle’s disease, this enzyme is either missing or non-functional. The result of this inability to metabolize glycogen properly is premature muscle fatigue and risk of muscle injury.
How many people have McArdle’s disease?
It is estimated that McArdle’s disease affects 1 in 100,000 individuals. However, since the disease remains undiagnosed in many people until they reach adulthood, that number may be higher.
What is glycogen?
Glycogen is a storage polymer of glucose. Muscles store glucose as glycogen in order to have immediate access to an abundant energy source during exercise. Glycogen is replenished within the cell after it is depleted, which only occurs after hours of physical activity like running. Marathon runners and athletes often consume large amounts of carbohydrates the day before an event in a practice known as “carbo loading,” intended to increase the muscles’ stores of glycogen and extend performance.
Is McArdle’s disease life-threatening?
McArdle’s disease is not by itself life-threatening, but muscle failure itself can be hazardous in a number of ways. Strenuous activities depend on glycogen metabolism, and without the energy to sustain such activities people with McArdle’s disease may find themselves unable to finish what they have started. While swimming, chewing and swallowing food, an episode of muscle failure can be disastrous. People with McArdle’s disease should always remain aware of their limitations to avoid danger.
Is there a cure for McArdle’s disease?
There is no known cure for McArdle’s disease. A number of genetic mutations responsible for non-functioning or missing phosphorylase enzyme have been identified. To date, gene replacement therapies have not advanced beyond the experimental stage in animals.
How is McArdle’s disease treated?
Because the muscle injury that can occur with McArdle’s disease releases large amounts of protein into the blood, it can cause renal dysfunction and therefore demands medical attention. Such injuries, known as rhabdomyolysis, may be treated with intravenous saline. Refer to your physician for recommendations on treatment or if you have McArdle’s disease and want to take a pain relief medication. By avoiding such injuries and participating in a good diet and regular low-impact aerobic activity such as walking – with careful warmup periods – people with McArdle’s disease can remain quite healthy. Otherwise, there remains no consensus therapy for McArdle’s disease beyond diet and lifestyle management.