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DOES IT RUN IN THE FAMILY?
On being told they have a genetic disorder such as a metabolic muscle disease, bewildered patients often ask, "But it doesn't run in the family, so how could it be genetic?"
Metabolic myopathies can run in a family, even if only one person in the biological family has it. This is because of the ways in which genetic diseases are inherited.
Most of the metabolic diseases of muscle are inherited in an autosomal recessive pattern, meaning that a person needs two defective genes in order to have the disease. One copy is inherited from each parent, neither of whom would normally have symptoms.
Thus, the disease appears to have occurred "out of the blue," but in reality, both parents may be carriers, silently harboring the genetic mutation (a flaw in the gene). Many parents have no idea they're carriers of a disease until they have a child who has the disease.
Other metabolic disorders have X-linked or autosomal dominant patterns of inheritance, each of which carries different risks for transmission to children. In some cases, a single disorder is associated with more than one pattern of inheritance.
Finally, metabolic disorders actually can occur "out of the blue" when a new mutation appears with a baby's conception. These are called spontaneous mutations, and, after they occur, they can be passed on to the next generation.
The risk of passing on a metabolic myopathy to your children depends on many circumstances, including exactly which type of metabolic disease has been diagnosed.
A good way to find out more about these risks is to talk to your MDA clinic physician or ask to see the genetic counselor at the MDA clinic. Also, see MDA's pamphlet, "Genetics and Neuromuscular Diseases."
Facts About Metabolic Diseases of Muscle
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