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A metabolic myopathy is a genetic disorder that interferes with the complex metabolic processes that provide the muscles with energy to function. Some examples include lactate dehydrogenase deficiency, debrancher enzyme deficiency, and carnitine deficiency. These conditions cause muscle pain and weakness after relatively short episodes of exercise and can also predispose patients to the risk of issues like cardiovascular disease and adverse reactions to anesthesia.
In some cases, a metabolic myopathy is the result of a spontaneous mutation in the genes of one of the patient’s parents. Other cases involve inherited genes, sometimes recessive traits that parents may not have been aware of before a pregnancy. Diagnosis of a metabolic myopathy can be a complex process. These conditions are sometimes mistaken for muscular dystrophies or other disorders, and extensive testing and evaluation may be necessary to identify the problem and determine which enzyme deficiency is involved.
The body relies on a series of chemical reactions to turn nutrients into energy the muscles can use for power. A deficiency in any one of the enzymes involved in this process can limit the amount of energy available to the muscles; in a metabolic myopathy, the muscles may not be able to store glycogen, for example. When the patient starts demanding power from the muscles, they quickly run out of resources and may start cramping and seizing.
These conditions are not curable because they involve a fundamental genetic problem that is beyond repair. They can be managed, however. Changing a patient’s diet and exercise habits may address the issue. Patients may need to avoid particular activities that could strain their muscles, and could find it helpful to eat or avoid certain foods to support metabolic functions. The patient will need monitoring for life to address the disorder.
People with metabolic myopathy or a family history of this issue may want to discuss it with a genetic counselor if they want to have children. The risks for passing the disease on can vary, depending on the nature of the condition and the genetic makeup of the parents. Organizations dedicated to various muscle myopathies can provide advice and information as well as access to clinical trials and other resources patients and their families may find helpful. Support groups can also offer assistance for parents concerned about genetic risks who want a chance to interact with people who have these disorders so they can learn more about what to expect.