A muscle biopsy will help in the diagnosis. It involves taking a small sample of muscle and studying its structure under the microscope (read our Muscle biopsies factsheet for more information).
Muscle affected by GNEM has a characteristic appearance under the microscope; there are circular structures called ‘rimmed vacuoles’ inside the muscle cells.
Your consultant may wish to carry out magnetic resonance imaging (MRI) on the leg muscles to see which muscles are affected and to what extent. If the pattern of muscle involvement on MRI is typical for GNEM, this can be helpful in recognising the condition earlier, and therefore requesting gene testing earlier. The MRI scan is non-invasive and painless, and is becoming more widely used to test for various muscle disorders.
A genetic test is essential to confirm a diagnosis of GNEM. This involves having a small sample of blood taken and sent off to a diagnostic laboratory. There, they will extract DNA from the blood and test it for the presence of mutations in GNE. For more information, please read our Diagnostic tests factsheet.