Last updated Jan. 12, 2022, by Marisa Wexler, MS
Fact-checked by José Lopes, PhD
Muscular dystrophies are a group of genetic diseases that cause progressive muscle weakness and wasting. A range of tests may be helpful in diagnosing specific types of muscular dystrophy, one of which is muscle biopsy.
What is a muscle biopsy?
In simplest terms, a muscle biopsy involves collecting a small sample of muscle tissue, which is then examined by specialists in a lab. The biopsy typically is collected from a muscle that is moderately affected by the suspected condition.
Biopsies are usually done while the patient is awake, with local anesthesia to minimize discomfort. The sample can be collected in two ways: a needle biopsy or an open biopsy.
In a needle biopsy, a small muscle sample is collected through a needle, which is inserted into the muscle. It is a quick procedure, typically lasting only about 10 minutes, and it leaves a small scar. Since it’s less invasive than open biopsy, needle biopsy is usually preferred in modern medical practice.
However, it only collects a small quantity of muscle tissue, which may not be enough for some types of analysis. In these cases, additional needle biopsies or open biopsy may be needed to get sufficient tissue.
An open biopsy involves making a cut through the skin to retrieve a muscle sample. The patient may require stitches afterward, as the incision is usually several centimeters long. Open biopsies can be completed on any muscle and will provide enough specimen for most assessments.
How is the sample analyzed?
Once harvested, the biopsy sample is sent to a laboratory, frozen, and cut into thin slices that experts can then examine in detail under a microscope. In muscular dystrophy patients, this can be used to identify structural damage to the muscle fibers.
The analysis also often includes using specialized reagents to dye certain components of the cell. For example, biopsies can be assessed for the amount of dystrophin protein contained in muscle tissues — this protein is absent in the most common form of muscular dystrophy, Duchenne muscular dystrophy, and is present at lower-than-normal levels in another type called Becker muscular dystrophy.
Muscle biopsy generally is considered a safe procedure with minimal associated risks. Patients will often experience some bruising and discomfort at the biopsy site, especially if an open biopsy is used. Pain-relieving medications may be given for a few days after a biopsy is collected.
Biopsies can result in bleeding at the biopsy site, which is typically minor. People with a a history of bleeding disorders or taking blood-thinning medicines need to disclose such conditions or treatments to their healthcare provider. They may have to stop these therapies before the procedure.
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