Genetic testing may be useful for prospective parents who have a family history of MD and are worried about passing the condition on.
Speak to your GP, who can refer you for genetic screening and counselling.
Genetic testing can be used to:
- identify carriers of the condition
- perform a prenatal diagnosis (where a foetus is tested during pregnancy)
Some types of MD are carried without causing clear signs of the condition. This applies to recessive inherited disorders, sex-linked conditions and even some dominant conditions (particularly myotonic dystrophy). Genetic testing can determine who is carrying the disorder. Read more about the causes of muscular dystrophy.
For example, a woman with a family history of Duchenne MD but no symptoms herself may be carrying the gene that causes it. DNA can be taken from cells in the blood, saliva or tissue. The DNA in the relevant gene can then be tested to find out if she is carrying the faulty gene.
If you or your partner are a carrier of MD and are at risk of passing the condition on to your child, your genetic counsellor will discuss your options with you.
Genetic testing can be used for prenatal diagnosis. This is when a baby is diagnosed with MD before it is born, using tests that are carried out during pregnancy. If you are pregnant and there is a possibility that your unborn baby has MD, you may be offered tests.
There are two main ways of performing these tests. One is chorionic villus sampling (CVS). This is when tissue from the placenta is removed for analysis early. This is often at less than 11 weeks into the pregnancy.
The other method is amniocentesis, which is not usually carried out until 15-16 weeks. In amniocentesis a needle is inserted into your abdomen to take a sample of amniotic fluid (the fluid that surrounds the foetus in the womb). This fluid contains cells that have been shed by the foetus. Both tests carry a risk of causing miscarriage.
The cells from the foetus can be tested to determine whether they have the genetic mutation that is responsible for MD. If they do, the baby is likely to develop MD at some stage after birth. If this is the case your genetic counsellor will be able to discuss your options with you.
Be aware that there are limitations to this kind of diagnosis. Tests can give misleading results or unexpected, unanticipated results. It is important to discuss prenatal testing and the meaning of the possible results before going ahead with the procedure.
A normal test result does not ensure that the baby will be healthy. The test only looks for the particular type of MD in the family but not for all other possible problems. Prenatal diagnosis can only be performed if there is a precise genetic diagnosis of the family's condition.