Metabolic myopathies are rare, genetic disorders that cause muscle problems. “Metabolic” refers to chemical reactions that provide necessary energy and nutrients for healthy muscle growth. Metabolic myopathies are inherited and tend to run in families. They can occur at any age. Genetic defects interfere with the processes in muscle that generate energy. Muscle cells cannot work properly. To work properly, muscles need a chemical called adenosine triphosphate (ATP). Cells make ATP from sugars and fats on certain pathways in chemical reactions driven by enzymes. Lack of certain enzymes causes metabolic myopathies, which are named according to the pathways affected. Some myopathies can cause rhabdomyolysis (a process when muscle tissue gets damaged and substances from inside the muscle cells enter the bloodstream).
What Are the Signs/Symptoms?
Symptoms of metabolic myopathies include muscle weakness, tiring after exercise or activity, muscle pain after any physical effort, and swollen or tender muscles. Some people with metabolic myopathies never have symptoms. Other pathways in their body make the ATP necessary for muscles to work when one pathway does not work. When the body needs to make more energy from that pathway, an ATP deficit can develop and cause symptoms. If cells are moderately low in ATP, signs are fatigue or exercise intolerance. Rhabdomyolysis, or the death of muscle cells, occurs when cells do not have enough ATP. Low-grade rhabdomyolysis may cause constant weakness. A rheumatologist can diagnose metabolic myopathies with a muscle tissue biopsy or genetic testing. With a biopsy, a needle is used to remove a small sample of tissue.
What Are Common Treatments?
Treatments vary according to the patient’s particular myopathy. Treatments include changes in physical activity and diet, aerobic and anaerobic (resistance) exercise training, and the use of various vitamins and supplements. The goal of treatment is to control symptoms and minimize progression of muscle weakness. Physical and occupational therapy are often important in the management of metabolic myopathies.
Living with Metabolic Myopathies
Treatment for metabolic myopathies varies by myopathy, but is focused on changes in physical activities, aerobic exercise training, changes in diet, and the use of various vitamins or supplements. With appropriate activity changes, regular aerobic exercise, diet and use of supplements, the symptoms often can be controlled. The diet, levels of physical activity and dietary supplements recommended for treatment will vary depending on myopathy.
Updated February 2023 by Kristen Lee, MD, and reviewed by the American College of Rheumatology Committee on Communications and Marketing.
This information is provided for general education only. Individuals should consult a qualified health care provider for professional medical advice, diagnosis and treatment of a medical or health condition.