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Duchenne muscular dystrophy (DMD) – information for carriers

  • Muscular dystrophies (MD) are common neuromuscular (nerve and muscle) disorders, characterised by loss of muscle strength and bulk. Duchenne (doo-shen) muscular dystrophy (DMD) is the most common type of muscular dystrophy, affecting about one in every 3500 boys. 

    DMD is caused by a gene change or alteration, called a genetic mutation, in the dystrophin gene on the X chromosome. 

    DMD can occur randomly in a family or be inherited. Females are not usually affected by the symptoms of DMD, but can be carriers of the condition and pass it on to their children. Some carriers experience mild symptoms such as muscle weakness or cramping. Female carriers of DMD are also at risk of developing cardiomyopathy (disease of the heart muscle) and should be reviewed by a cardiologist every few years.

    How is DMD inherited?

    DMD is inherited in a pattern called X-linked recessive. This means that almost all affected individuals with DMD are male, while females can be carriers. The son of a carrier mother has a 50 per cent chance of being affected, while the daughter of a carrier mother has a 50 per cent chance of being a carrier too. It is extremely rare for females to be affected, though this can occur when a mother is a carrier and a father is affected. A carrier daughter can show very mild symptoms but often only discovers their carrier status when an affected son is born.

    Signs and symptoms of DMD mutations

    Female carriers with DMD mutations usually show no symptoms of the condition. However, some experience muscle pain and cramps with physical exertion, or muscle weakness in the limbs. Symptoms, if they occur, may happen at any time in life.

    Heart problems in female carriers are usually mild and limited to changes that are noticed during a test called an echocardiogram (echo), which is an ultrasound looking at the heart muscle.

    When to see a doctor

    The following people should have genetic counselling and testing for DMD mutations:

    • adult females (e.g. sisters, mothers and aunts) closely related to anyone with DMD
    • first-degree relatives (e.g. mothers, children or siblings) of female carriers.

    This testing is not routinely offered to children, as they are too young to give their informed consent to the test. However, you can begin talking to your daughter about the need for testing and the consequences of being found to be a carrier from mid to late adolescence. 

    Treatment for carriers of DMD

    • For girls who are closely related to boys with DMD, education should be started in mid to late adolescence regarding the risk of developing cardiomyopathy, and the signs and symptoms of heart disease.
    • Female carriers should have regular check-ups for development of cardiomyopathy. In females who have changes on their echo, a family history of heart disease, or additional lifestyle risk factors (e.g. smoking, obesity), the cardiologist may recommend more frequent monitoring.
    • Even if they have no symptoms, female carriers should consider having cardiac testing before becoming pregnant, or when a pregnancy is discovered.  
    • Treatment for female carriers who are experiencing symptoms or cardiac disease is similar to the treatment of DMD. See our fact sheet Duchenne muscular dystrophy (DMD).

    Key points to remember

    • Female carriers of DMD mutations do not usually have symptoms. 
    • Symptoms vary, but may include muscle pain and cramps with physical exertion, severe muscle weakness and dilatation of the heart. 
    • Female relatives of children with DMD should have their carrier status tested. 
    • All at-risk females, regardless of their carrier status, should be monitored for development of cardiomyopathy.

    For more information

    Common questions our doctors are asked

    If my daughter is a DMD carrier, how likely is it that her future children will have DMD?

    If your daughter has a son, there is a 50 per cent chance they will have DMD. If your daughter has a daughter, there is a 50 per cent chance they will be a carrier too.

    What can I do about my daughter's muscle pain and cramps?

    If a female carrier is experiencing symptoms, the treatment is the same as for people with DMD and may include physiotherapy and/or corticosteroid medication. 


    Developed by The Royal Children's Hospital Neurology department. We acknowledge the input of RCH consumers and carers.

    Reviewed June 2018.

    This information is awaiting routine review. Please always seek the most recent advice from a registered and practising clinician.

    Kids Health Info is supported by The Royal Children’s Hospital Foundation. To donate, visit www.rchfoundation.org.au.


Disclaimer

This information is intended to support, not replace, discussion with your doctor or healthcare professionals. The authors of these consumer health information handouts have made a considerable effort to ensure the information is accurate, up to date and easy to understand. The Royal Children's Hospital Melbourne accepts no responsibility for any inaccuracies, information perceived as misleading, or the success of any treatment regimen detailed in these handouts. Information contained in the handouts is updated regularly and therefore you should always check you are referring to the most recent version of the handout. The onus is on you, the user, to ensure that you have downloaded the most up-to-date version of a consumer health information handout.