Type V glycogen storage disease
Myophosphorylase deficiency; Muscle glycogen phosphorylase deficiency; PYGM deficiencyType V (five) glycogen storage disease (GSD V) is a rare inherited condition in which the body is not able to break down glycogen. Glycogen is an important source of energy that is stored in all tissues, especially in the muscles and liver.
GSD V is also called McArdle disease.
Causes
GSD V is caused by a flaw in the gene that makes an enzyme called muscle glycogen phosphorylase. As a result, the body cannot break down glycogen in the muscles.
Enzyme
Enzymes are complex proteins that cause a specific chemical change. For example, they can help break down the foods we eat so the body can use them....
Read Article Now Book Mark ArticleGSD V is an autosomal recessive genetic disorder. This means to have the disorder, you must receive a copy of the nonworking gene from both parents. A person who receives a nonworking gene from only one parent usually does not develop this syndrome. A family history of GSD V increases the risk.
Autosomal recessive
Autosomal recessive is one of several ways that a genetic trait, disorder, or disease can be passed down through families. An autosomal recessive dis...
Read Article Now Book Mark ArticleSymptoms
Symptoms commonly start during early childhood. But, it may be difficult to separate these symptoms from those of normal childhood. Diagnosis may not occur until a person is over 20 or 30 years old.
- Burgundy-colored urine (myoglobinuria)
- Fatigue
- Exercise intolerance, poor stamina
- Muscle cramps
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Muscle pain
Muscle pain
Muscle aches and pains are common and can involve more than one muscle. Muscle pain also can involve ligaments, tendons, and fascia. Fascias are th...
Read Article Now Book Mark Article - Muscle stiffness
- Muscle weakness
Exams and Tests
The following tests may be performed:
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Electromyography (EMG)
Electromyography (EMG)
Electromyography (EMG) is a test that checks the health of the muscles and the nerves that control the muscles.
Read Article Now Book Mark Article - Genetic testing
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Lactic acid in blood
Lactic acid in blood
Lactic acid is mainly produced in muscle cells and red blood cells. It forms when the body breaks down carbohydrates to use for energy when oxygen l...
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MRI
MRI
A magnetic resonance imaging (MRI) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the body. It does not us...
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Muscle biopsy
Muscle biopsy
A muscle biopsy is the removal of a small piece of muscle tissue for examination.
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Myoglobin in urine
Myoglobin in urine
The myoglobin urine test is done to detect the presence of myoglobin in urine. Myoglobin can also be measured with a blood test.
Read Article Now Book Mark Article - Plasma ammonia
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Serum creatine kinase
Serum creatine kinase
Creatine phosphokinase (CPK) is an enzyme in the body. It is found mainly in the heart, brain, and skeletal muscle. This article discusses the test...
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Treatment
There is no specific treatment.
The health care provider may suggest the following to stay active and healthy and prevent symptoms:
- Be aware of your physical limitations.
- Before exercising, warm up gently.
- Avoid exercising too hard or too long.
- Eat enough protein.
Ask your provider if it's a good idea to eat some sugar before exercising. This may help prevent muscle symptoms.
If you need to have surgery, ask your provider if it's OK for you to have general anesthesia.
Support Groups
More information and support for people with type V glycogen storage condition and their families can be found at:
- Association for Glycogen Storage Disease -- www.agsdus.org
- Genetic and Rare Diseases Information Center (GARD) -- rarediseases.info.nih.gov/diseases/6528/glycogen-storage-disease-type-5
Outlook (Prognosis)
People with GSD V can live a normal life by managing their diet and physical activity.
Possible Complications
Exercise may produce muscle pain, or even a breakdown of skeletal muscle (rhabdomyolysis). This condition is associated with burgundy-colored urine and a risk for kidney failure if it is severe.
Rhabdomyolysis
Rhabdomyolysis is the breakdown of muscle tissue that leads to the release of muscle fiber contents into the blood. These substances are harmful to ...
Read Article Now Book Mark ArticleKidney failure
Acute kidney failure is the rapid (less than 2 days) loss of your kidneys' ability to remove waste and help balance fluids and electrolytes in your b...
Read Article Now Book Mark ArticleWhen to Contact a Medical Professional
Contact your provider if you have repeated episodes of sore or cramped muscles after exercise, especially if you also have burgundy or pink urine.
Consider genetic counseling if you have a family history of GSD V.
References
Hijazi G, Kishnani PS. Defects in metabolism of carbohydrates. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 107.
Kishnani PS. Glycogen storage diseases. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 191.
Williams LM, Mcdonald CM. Myopathic disorders. In: Cifu DX, ed. Braddom's Physical Medicine & Rehabilitation. 6th ed. Philadelphia, PA: Elsevier; 2021:chap 42.
Review Date: 12/31/2023
Reviewed By: Anna C. Edens Hurst, MD, MS, Associate Professor in Medical Genetics, The University of Alabama at Birmingham, Birmingham, AL. Review provided by VeriMed Healthcare Network. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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