Last updated Jan. 6, 2022, by Marisa Wexler, MS
Fact-checked by José Lopes, PhD
Muscular dystrophies are caused by genetic mutations — errors in the “code” contained in a person’s DNA. Genetic testing, as the term suggests, involves analyzing a person’s DNA in order to detect disease-causing mutations. This type of testing typically is done with cells in a blood, tissue, or saliva sample.
When is genetic testing used?
Genetic testing can be used to confirm a diagnosis of muscular dystrophy by identifying a mutation known to cause a particular type of the condition. Importantly, many tests look only for known mutations associated with a specific type of disease, so multiple tests may be needed to rule out different conditions. Additionally, tests may fail to identify mutations that have not been seen previously.
Sometimes, genetic testing is carried out during a pregnancy to determine whether the fetus has inherited a dystrophy-causing gene. This is called prenatal genetic testing, and it can be performed though either chorionic villus sampling (CVS) or amniocentesis. These two methods differ in the way a cell sample is collected: CVS is typically done approximately 11 weeks into the pregnancy, and involves collecting tissue from the placenta for analysis. Amniocentesis usually is done around week 15 of the pregnancy, and using a long needle inserted through the woman’s abdomen to collect fluid from around the developing fetus for analysis.
Depending on the genetics underlying the specific condition, an individual can have a dystrophy-causing mutation, but show no symptoms of the disease. Such individuals are said to be “carriers,” because they don’t have the disease themselves, but they can pass the disease-causing mutation to their biological children, who may be carriers themselves or may develop the disease. Genetic testing may be used to identify disease carriers, particularly if a person has a family history of muscular dystrophy.
Risks associated with genetic testing
Prenatal testing is associated with a small risk of miscarriage, affecting approximately one-in-200 to one-in-400 pregnancies.
There are no major health risks associated with diagnostic genetic or carrier detection testing. However, undergoing this kind of testing often is daunting and stressful, and the results of specific tests may be complex and hard to understand without expertise. Genetic counseling is widely recommended to help in navigating these issues.
What is genetic counseling?
Genetic counseling is the process of helping people better understand the medical, psychological, and familial implications of a genetic disease. It is performed by specialists known as genetic counselors or by clinicians trained in human genetics.
Genetic counselors act as an interface between the patient and the clinician by recommending the appropriate genetic tests required to diagnose and confirm muscular dystrophy, along with helping to understand the results of such tests. Genetic counselors explain to patients and their healthcare providers the likelihood of the disease being passed to the next generation, and can help with family planning.
An important aspect of genetic counseling is to offer emotional support to families. Counselors can provide referrals for community help groups and support services to help families cope with the challenges that living with muscular dystrophy can bring.
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