Last updated Jan. 6, 2022, by Marisa Wexler, MS
Fact-checked by José Lopes, PhD
Muscular dystrophy (MD) refers to a group of genetic disorders that cause progressive weakness and loss of muscle mass.
Blood samples are often taken early in cases of suspected MD, because they are a relatively easy way to begin working toward a diagnosis. Blood samples can be used to check for markers of muscle damage, and also for genetic tests.
Markers of muscle damage
When muscle cells become damaged, certain proteins that normally are found inside muscle cells can leak out into the bloodstream. As such, higher-than-normal levels of these proteins in the blood are indicative of muscle damage. The most widely used muscle damage markers are creatine kinase (CK, also sometimes called creatine phosphokinase) and aldolase.
Elevated levels of these proteins in the blood, suggesting muscle damage, are characteristic of (though not specific to) MD. High levels of these proteins may be present before symptoms become apparent. However, measuring these proteins does not provide reliable information about the cause of muscle damage, but merely that muscle damage is occurring.
In early stages of MD, levels of these markers are generally higher than in later stages. This is likely because muscle degeneration is more rapid in earlier stages and because of declines in total muscle mass over time as the disease progresses.
A blood sample is frequently used for genetic testing to detect the specific mutation(s) that cause a particular type of muscular dystrophy. There are a variety of types of genetic tests, but broadly, all of them involve analyzing the sequence of a person’s genes to look for MD-causing mutations.
In addition to diagnostics, genetic testing also may be useful in research, and it can be used to identify carriers — people who have a mutated gene that isn’t causing disease, but who may pass the mutation to their biological children.
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