QUICK GUIDE – Diagnosis of DMD

If your doctor suspects DMD, it is very important to find a correct diagnosis as quickly as possible. He or she will refer you to a neuromuscular specialist, who will evaluate your child. The first step is a clinical evaluation, including:

  • A physical exam, to inspect muscle strength and development
  • A family history, to detect family members who carry the dystrophin gene

The second step is further testing:

  • A repeat blood test may be ordered to measure your child’s muscle protein creatine kinase (CK) level.
  • A muscle biopsy may take a small muscle sample for analysis to obtain information on the amount of dystrophin in muscle cells
  • A genetic test on a blood sample will provide specific and detailed information about DNA changes (mutations) that confirm a diagnosis of DMD

What you need to know about diagnostic tests

The normal range of CK is 60 to 400 units/liter. Children with DMD have a CK rate 10 to 200 times higher than average. A very high rate of CK informs the doctor that the child has a muscle disease (myopathy). In order to tell if the muscle disease is DMD, the doctor orders other tests — a genetic test or a muscle biopsy.

To confirm a diagnosis of DMD, genetic testing is the best choice. After a muscle biopsy, a genetic test is necessary to identify the specific DNA change (mutation) causing DMD. However, if a genetic test confirms a diagnosis of DMD, a muscle biopsy may not be necessary.

Genetic testing

If the child has a high CK level, your doctor may order a genetic test on a blood sample to identify genetic changes (mutations) that cause DMD. It may take several weeks or even months to get the results. If the test detects a genetic mutation that causes DMD, then the child is diagnosed with DMD.

It is important for a neuromuscular specialist to interpret the test results. He or she can refer you to another specialist for genetic counseling (see below).

Different types of genetic tests can provide specific and detailed information about your child’s DNA changes (mutations). Knowing your child’s exact mutation is key to future treatment.

Learn more about diagnosis & genetic testing here.

Decode Duchenne

Hospitals are usually able to provide genetic testing. Or, you can turn to Decode Duchenne for free genetic testing and counseling for people with DMD or Becker muscular dystrophy (MD).

To participate in Decode Duchenne, patients must:

  • Have a confirmed or suspected diagnosis of DMD or Becker MD, based on their doctor’s evaluation, clinical symptoms and a positive test for creatine kinase
  • Have not participated in other diagnoses or had previous genetic testing to confirm a DMD gene mutation
  • Face a financial barrier to genetic testing
  • Be citizens or legal residents of Canada or the USA

Talk to your doctor about Decode Duchenne, exchange information and ask questions about the program.

Contact Decode Duchenne: coordinator@duchenneconnect.org [insert link]

Muscle biopsy

If the child has a high CK level and signs of DMD, but genetic tests did not find a genetic mutation for DMD, the child may need to have a muscle biopsy. During this minor surgery, the doctor will remove a small sample of the child’s muscle. The sample is sent to a laboratory, which analyzes how much dystrophin is found in the muscle cells. If the child’s muscle sample has no dystrophin, then he is diagnosed with DMD.

Not all people with DMD need a muscle biopsy. Encourage your doctor to order genetic testing first and use a genetic testing plan to reduce the chance that the child will need a muscle biopsy.

Genetic counseling and carrier testing

YOU ARE NOT ALONE. Consult your doctor if you have any questions about genetic testing. Your neuromuscular specialist can refer you for genetic counseling. Make an appointment with a geneticist.

The mother of a child with DMD should ask for genetic testing to check whether or she carries the same DNA changes. A mother who has the mutation is called a carrier. She can pass the defective gene to her sons, who will develop DMD, and her daughters, who will become carriers as well.

With this information, a mother can make informed decisions about future pregnancies. And, other female family members on the mother’s side (sisters, daughters, aunts, and cousins) can be tested to discover if they carry the mutation.

What happens next?

After diagnosis, doctors, specialists, genetic counselors and patient support groups can help family members can learn more about DMD, including its development, the general course of the disease, and different types of treatment. Your doctors can begin an appropriate therapeutic monitoring plan, and family members can arrange to receive support and training.