DMD-related dystrophinopathy (including Duchenne/Becker muscular dystrophy and dilated cardiomyopathy)

Dystrophinopathy is a family of disorders that cause muscle weakness, often in the skeletal system and heart.

Duchenne muscular dystrophy (DMD) is the most serious form of the disease. DMD presents in early childhood with delayed sitting and standing, muscle weakness, and some cognitive impairment. The muscle disease gets worse quickly, and affected individuals are typically wheelchair-bound by age 13. Heart disease known as dilated cardiomyopathy, or DCM, usually occurs by age 18 and unfortunately, death from heart or respiratory complications often occurs by early adulthood.

Becker muscular dystrophy (BMD) is a later-onset form of the condition, and is also characterized by muscle weakness and heart disease. Symptoms of BMD begin later and may be more mild. Life expectancy for patients with BMD varies.

Dystrophinopathy is X-linked and primarily affects males. Female carriers are not usually affected, though some may have symptoms, including muscle weakness and cramping, and increased risk of developing DCM.

Some affected individuals may have DCM but not experience muscle weakness. In males, the onset of DCM is usually between ages 20 and 40, and can cause rapid decline. Onset in symptomatic females is typically later and progression of the disease is generally slower. Treatment for dystrophinopathy is focused on managing the individual's symptoms and monitoring for heart disease.

Quick facts about DMD-related dystrophinopathy (including Duchenne/Becker muscular dystrophy and dilated cardiomyopathy)
Genes: DMD
Inheritance: X-linked
Relevant resources for DMD-related dystrophinopathy (including Duchenne/Becker muscular dystrophy and dilated cardiomyopathy)

A quick genetics rundown

As humans we have about 23,000 genes. These genes are like tiny instruction manuals that influence our health, growth and development. We inherit half of our genes from our biological mum and the other half from our biological dad. These genes are lined up on structures called chromosomes. Most of us have 23 pairs of chromosomes. The first 22 pairs are called autosomes and for the most part - these are the same among men and women. The 23rd pair determine our sex - two X chromosomes for a female and one X and one Y chromosome for males.

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How is DMD-related dystrophinopathy (including Duchenne/Becker muscular dystrophy and dilated cardiomyopathy) inherited?

DMD-related dystrophinopathy (including Duchenne/Becker muscular dystrophy and dilated cardiomyopathy) is an X-linked condition. X-linked conditions occur when there is a genetic variation on the X-chromosome. For these conditions, the sex of the parent who passes on the gene variation influences the risk for the children.

If the father is affected, all his daughters will have a variation on one of their X-chromosomes and be healthy carriers. Sons can only inherit these x-linked conditions from their mother and therefore, in this situation, will not be affected by the disease.

If the mother is a healthy carrier of an X-linked variation and has a son, there is a 50% chance that they could inherit this variant and be affected by the disease. If they have a daughter, there is a 50% chance that they will be a healthy carrier (just like her mum).

Another way of looking at this is that there is a 25% chance of having an affected son and a 75% chance that the child will not be affected by the disease.

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What is carrier screening?

Carrier testing is like a checkup for your genes. It tests to see if you carry a gene variation that could cause a serious genetic disease in your child. Eugene offers an inclusive genetic carrier screening panel that includes DMD-related dystrophinopathy (including Duchenne/Becker muscular dystrophy and dilated cardiomyopathy), but there's a total 301 conditions that can be tested.

Eugene’s carrier test is a clinical grade test that can be done from the comfort of your own home — it’s just a saliva test. You're also paired with a genetic counsellor who provides mindful support and guidance every step of the way.

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Should parents screen for DMD-related dystrophinopathy (including Duchenne/Becker muscular dystrophy and dilated cardiomyopathy) before or early in pregnancy?

The biggest benefit of screening for DMD-related dystrophinopathy (including Duchenne/Becker muscular dystrophy and dilated cardiomyopathy) is that it can help future parents understand their reproductive risk so they can be ready and empowered to make more informed decisions. If neither partner are carriers, it provides reassurance and peace of mind that the risk of having a child with a genetic disease is low.

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