La muscle biopsy is an examination that involves removing a piece of muscle to examine it.

Muscle biopsy is done with the aim of identifying or detecting many conditions, including:

• of the connective tissue and blood vessel diseases
• infections that affect muscles, such as Toxoplasmosis
• muscle disorders, such as muscular dystrophy or a congenital myopathy
• or a metabolic defect muscle (metabolic myopathies).

The muscle biopsy is performed in a specialized center. The doctor performs a local anesthesia on the skin, at the level of the sampling site, before performing the biopsy. The choice of muscle to biopsy is guided by the clinical examination of the physician and may require theusing an MRI or muscle scanner prior. Note that the muscle that will undergo a biopsy must show symptomatic damage, but must not be too damaged, so that the doctor can obtain enough tissue to analyze.

A first type of biopsy involves inserting a needle into the (superficial) muscle and removing it quickly as soon as a piece of muscle has been removed.

A second type involves making an incision (1,5 to 6 cm) in the skin and muscle to remove a piece of muscle tissue. A suture is made to close the incision. It is not necessary to be on an empty stomach. The side effects are not significant, usually a bruise and a feeling of stiffness.

The collected muscle pieces are finally sent to the laboratory for analysis (study of muscle tissue under a microscope, analysis of muscle proteins by immunohistochemistry, genetic analyzes, etc.). Examination under a microscope can identify the type of lesions (signs of necrosis may be visible in particular).

Muscle biopsy can help the doctor diagnose the following conditions, including:

• a atrophy (loss of muscle mass)
• a inflammatory myopathy (inflammation of muscle tissue)
• a Duchenne muscular dystrophy (inherited disease characterized by weakening and degeneration of muscle cells due to a lack of the protein dystrophin) or other genetic myopathy
• a muscle necrosis

Depending on the results, the doctor may therefore detect a disease and may suggest an adequate treatment or appropriate management.