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McArdle disease: Causes, Symptoms, Diagnosis and Treatment

Aug 11, 2023

McArdle disease: Causes, Symptoms, Diagnosis and Treatment

McArdle disease is a rare muscular disorder. The complex substance known as glycogen cannot be broken down by the muscle cells in this situation. It is a member of the group of diseases known as glycogen storage disorders. The McArdle disease is also known as glycogen storage disorder type 5 (GSD 5, sometimes known as GSD V).

A simple molecule called glucose gives your cells energy. After you eat, your digestive system releases a large amount of glucose into your blood. As a result, your blood glucose levels rise. Your body removes this extra glucose from the blood to keep blood glucose levels steady. Your body then transforms the excess glucose into glycogen. The muscles, liver, and other organs of the body store it.

The glucose level in your blood starts to fall after a long period of fasting. This instructs your body to begin utilizing part of the earlier-stored glycogen. To provide a constant supply of glucose for your body, glycogen is converted into glucose.

To continue functioning properly, your muscles require a steady supply of glucose. Your muscles are unable to break down the stored glycogen if you have McArdle illness. That's because your muscle cells lack a crucial component required for that procedure. This means that your muscles cannot obtain the glucose they require from the stored glycogen. Myophosphorylase is an enzyme that is crucially lacking in your muscles.

An enzyme is a substance that helps the body's chemical processes go along more quickly.

You could find it difficult to exercise as a result to avoid getting weary and experiencing muscle soreness. The majority of the time, this health issue's symptoms start to show up by the time a person is 15 years old.

Causes Of McArdle’s Disease

The condition known as McArdle disease is hereditary. It originates from modifications (mutations) in the gene for the enzyme muscle phosphorylase. This enzyme cannot be produced by muscle cells. Consequently, they are unable to convert glycogen to glucose. For optimal performance, your muscles require glucose.

A parent frequently transmits a gene alteration that results in McArdle disease to a kid. For each substance your body produces, you typically have a pair of genes (one from each parent). A person with McArdle disease often requires 2 copies of a gene that has been altered. This is a recessive inheritance.

Even if a person only carries one copy of the defective gene, they may still experience certain McArdle disease symptoms.

Symptoms Of McArdle’s Disease

Muscle signs and symptoms are brought on by McArdle disease. In general, it could make it difficult for you to work out without getting exhausted. Walking slowly might prevent this from happening. But if you do it for longer than a few minutes, it can be difficult for you. 

You might see that after a brief pause, you have a "second wind" that enables you to work out once again. The severity of these symptoms can change. The following are some typical signs and symptoms of McArdle disease:

  • After 8 to 10 minutes, you're better able to perform aerobic exercise (second-wind phenomena).
  • Especially after periods of activity, urine that is brownish red
  • Easily exhausted by action, with stiffness or weakness immediately after beginning exercise
  • Cramping in the muscles
  • Pain in the muscles
  • Lasting (permanent) weakening of the thigh muscles or other muscles. A limited percentage of those who have the disorder experience this.
  • People typically become aware of these symptoms prior to the age of 15. People frequently presume the symptoms are "growing pains" or the result of another factor. The degree of a person's symptoms can vary. You can even observe that the symptoms seem to get worse or better at different times.

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Diagnosis Of McArdle’s Disease

Your healthcare professional starts by asking about your medical history. They enquire about your current symptoms, previous medical issues, and family history of illnesses. They typically perform a complete physical examination that includes testing of your muscle strength. They could put your capacity for extended activity to the test. Several diagnostic procedures include:

  • Blood tests to look for muscle enzymes like creatine kinase
  • Blood testing for known McArdle disease mutations
  • Measurement of muscle electrical activity using electromyography
  • Exercise test for the forearms
  • MRI scans of your muscles
  • Muscle biopsy to check for glycogen storage in the muscle cells
  • Pee tests to look for myoglobin, which makes the urine dark
  • Before seeing a specialist, such as a neurologist, you might first visit your primary healthcare practitioner. Although McArdle's illness is uncommon, the symptoms frequently present in children. Some persons with the illness don't get diagnosed until they are well into adulthood.

Treatment Of McArdle’s Disease

The McArdle disease has no known treatment. However, you might be able to adopt some diet and exercise techniques to help control the issue. Your body may benefit from a well-planned low- to moderate-intensity exercise program to make the most of your capacity to utilize glucose. The creation of this strategy should be done in collaboration with your doctor, though. When exercising excessively, patients with McArdle disease risk damaging their muscles and kidneys. To develop the appropriate care strategy for your circumstances, you can collaborate with your medical team. The following are some treatments for McArdle disease:

  • A diet high in carbs must be carefully monitored.
  • Supplements with creatine
  • Prior to exercising, consume the recommended amounts of sugar.
  • Moderate aerobic exercise program prescribed by a doctor
  • Many medications, including ACE inhibitors
  • A safe exercise program must be developed in collaboration with the patient's medical team for those who have McArdle disease. You might also bring up genetic counseling with the group for further details and assistance.

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