Causes GNE myopathy (GNEM)

GNEM is caused by mutations (a mutation is a mistake in a gene that leads to a disorder or condition) in the GNE gene, which contains the instructions to make an enzyme called glucosamine (UDP-N-acetyl)-2-epimerase/N-acetylmannosamine kinase.

This has a key role in the production of sialic acid in the body. Sialic acid is a sugar that gets incorporated into several molecules important for cell function, including proteins and lipids. The gene may also have other roles important for muscle contraction. (Studies are currently underway.)

People with GNEM have a deficiency of sialic acid in the muscle cells. Researchers don’t understand fully how this leads to muscle weakness, but it could be that insufficient sialic acid affects the function of certain proteins in the muscle.

How is it inherited?

GNEM is inherited in a ‘recessive’ manner, which means that both copies of the GNE gene have to be mutated for someone to have the condition. If only one copy of the gene is mutated, that person is a carrier and will not have symptoms. When two carriers have a child together, there is a:

  • 25 percent chance that the child will have inherited both mutated copies of the GNE gene and will develop GNEM
  • 50 percent chance that the child will inherit only one mutated copy and thus be a carrier
  • 25 percent chance that the child will inherit two healthy copies, so will neither have the condition nor be a carrier. 

For more information on inheritance, please read our Inheritance and genetics factsheet.

How will my children be affected?

Children of a person with a diagnosis of GNEM are likely to have one mutated copy of the GNE gene and thus be carriers. This means they won’t have GNE myopathy or any signs of muscle weakness. Carrier genetic testing is available to confirm the presence or absence of GNE mutations in your children. This could be advisable if you and your partner are close relatives. You can get a referral for genetic counselling through your GP.

For more information, see our Genetic counselling and family planning factsheets.