Signs and Symptoms

DMD is rarely diagnosed at birth. Typically, it is diagnosed when the child is between 2 and 5 years old.

When you are looking for signs that a child may have DMD, you should watch them running and getting up from the floor. Muscle weakness is more noticeable during these activities.

Symptoms can include:

  • Delay in the ability to sit and stand independently
  • Large calf muscles (pseudohypertrophy)
  • Trouble running and jumping
  • Unusual gait when walking
  • Using the Gower's Manouevre to get off the floor (where the child has to use their hands and arms to "walk" up their own body from a squatting position due to lack of hip and thigh muscle strength)

Testing For DMD

Usually two tests are needed to diagnose DMD.

The first test is a blood test to measure the amount of a substance called creatine kinase. Children with DMD always have a very high level of creatine kinase in their blood (10-100 times above normal).

Creatine kinase is an enzyme that is found in muscle cells in the body. If muscles are damaged, the muscle cells are broken open and their contents find their way to the bloodstream. Elevated levels can be the result of an acute muscle injury, or to a chronic condition, such as DMD.

If the creatine kinase level is found to be high, further tests are needed to see if this is because of DMD or another condition.

The second test in diagnosing DMD is a genetic tests. This is taken through a blood sample. 

This test looks for either large changes in the gene or looks at the sequencing of the gene.

Together these two tests can detect DMD in about 95% of patients.

A third test is required for a small number of patients. They have to have a muscle biopsy to confirm the diagnosis.

This involves taking a small piece of muscle under local anaesthetic and looking at muscle fibres under a microscope. It can be painful, but it is the only way to tell the level of dystrophin in the muscle for certain.