Summary about Disease
Deficiency of muscle phosphorylase, also known as McArdle's disease or glycogen storage disease type V (GSD V), is a rare genetic metabolic disorder affecting skeletal muscle. It is characterized by the body's inability to break down glycogen (stored glucose) in muscle tissue due to a deficiency in the enzyme muscle phosphorylase. This enzyme is crucial for providing energy during exercise.
Symptoms
Exercise intolerance: The primary symptom is muscle pain, cramps, and stiffness during exercise, particularly high-intensity or anaerobic activities.
"Second wind" phenomenon: After a period of rest during exercise, some individuals experience a lessening of symptoms, allowing them to continue exercising. This is thought to be due to the muscles utilizing blood glucose more effectively.
Myoglobinuria: Breakdown of muscle tissue (rhabdomyolysis) can lead to the release of myoglobin into the urine, causing it to be dark red or brown.
Fatigue: General tiredness and weakness, especially after exercise.
Muscle weakness: Can occur in severe cases.
Elevated creatine kinase (CK) levels: Blood tests typically show high CK levels, indicating muscle damage.
Nausea and Vomiting
Causes
McArdle's disease is caused by mutations in the PYGM gene. This gene provides instructions for making muscle phosphorylase. The condition is inherited in an autosomal recessive pattern, meaning that both parents must carry a copy of the mutated gene for their child to be affected.
Medicine Used
4. Medicine used There is no specific medication to cure McArdle's disease. Management focuses on lifestyle modifications and strategies to prevent symptoms:
Dietary modifications: A diet rich in carbohydrates before exercise may help. Some individuals benefit from taking creatine supplements and consuming branched-chain amino acids (BCAAs), but their effectiveness varies.
Vitamin B6 supplementation: Some individuals have experienced benefits from Vitamin B6 supplementation.
Medications to prevent kidney damage: In severe cases with rhabdomyolysis, medications may be needed to protect the kidneys.
Avoiding medications known to increase risk of muscle damage Certain statins and other drugs may need to be avoided or used with great caution
Is Communicable
No, McArdle's disease is not communicable. It is a genetic disorder and cannot be spread from person to person.
Precautions
Avoid strenuous exercise: Limit intense physical activity that triggers symptoms.
Gradual warm-up: Start exercise slowly and gradually increase intensity.
Maintain hydration: Drink plenty of fluids, especially during and after exercise.
Dietary management: Follow recommended dietary guidelines, including carbohydrate intake before exercise.
Listen to your body: Stop exercise immediately if you experience muscle pain, cramps, or weakness.
Medical alert bracelet: Consider wearing a medical alert bracelet indicating that you have McArdle's disease.
Communicate: Inform healthcare providers, including dentists and surgeons, about your condition.
How long does an outbreak last?
McArdle's disease does not have outbreaks in the traditional sense of an infectious disease. Symptom duration depends on the intensity and duration of exercise. Muscle pain and stiffness can last from minutes to hours after exercise. Myoglobinuria, if it occurs, may last for several days.
How is it diagnosed?
Blood tests: Elevated creatine kinase (CK) levels are a key indicator. Lactate levels during ischemic exercise test do not rise or show very low rises in affected individuals.
Muscle biopsy: A muscle biopsy can show an absence or significant reduction in muscle phosphorylase activity. It can also show excessive glycogen storage.
Genetic testing: Genetic testing can confirm the diagnosis by identifying mutations in the PYGM gene.
Ischemic forearm exercise test: This test measures lactate production in the arm muscles during exercise with restricted blood flow. Individuals with McArdle's disease typically show little or no increase in lactate.
Timeline of Symptoms
9. Timeline of symptoms
Childhood/Adolescence: Symptoms often appear during childhood or adolescence when children begin participating in more vigorous physical activities. Some individuals may not be diagnosed until adulthood.
Onset: Symptoms typically begin within minutes of starting strenuous exercise.
Progression: The severity of symptoms can vary. Some individuals experience mild symptoms, while others have more significant limitations.
Long-term: McArdle's disease is a lifelong condition, but symptoms can be managed with lifestyle modifications.
Important Considerations
Genetic counseling: Genetic counseling is recommended for individuals with McArdle's disease and their families to understand the inheritance pattern and recurrence risk.
Kidney protection: Individuals with McArdle's disease should be aware of the risk of rhabdomyolysis and take steps to prevent kidney damage.
Anesthesia: Special considerations are needed during anesthesia due to the risk of muscle breakdown.
Exercise planning: Work with a healthcare professional to develop a safe and effective exercise plan.
Support groups: Support groups can provide valuable resources and emotional support for individuals with McArdle's disease and their families.