Genetics

Dystonia is a Movement Disorder

Being informed about the genetics of dystonia can be important in the diagnosis and treatment process.

Individuals with dystonia may be concerned that their children are at risk of inheriting the disorder. There are forms of dystonia that are known to be genetic and forms that may or may not have a genetic component—researchers cannot confirm or rule it out at this time. Numerous genes have been linked to dystonia.

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A genetic counselor can help individuals and families learn about the genetics of dystonia and whether they are eligible for genetic testing. Researchers are actively seeking to better understand the genetics of all dystonia's and to identify dystonia-causing genes.

Click here for an article about genetic counseling from the Dystonia Dialogue newsletter.

If an individual has a form of dystonia that is known to be genetic then there is a chance that the person may pass the disorder on to his/her biological children. This is especially true if other family members exhibit symptoms or are already diagnosed.

Genetic dystonias that are known to run in families can include early onset dystonias, isolated (primary) cervical dystonia, dopa-responsive dystonias, myoclonus-dystonia, paroxysmal dystonia's/dyskinesias, rapid-onset dystonia-parkinsonism, X-linked dystonia-parkinsonism, and others.

However, not everyone who inherits a dystonia-causing gene will develop symptoms. Also, some people develop dystonia due to a genetic mutation without any apparent family history. And to complicate things further, there are families in which many members are diagnosed with dystonia but no specific genetic mutation has yet been identified.

If an individual’s dystonia is secondary to an injury to the brain or nervous system (including exposure to certain medications or stroke), his/her children may not necessarily be at increased risk of developing dystonia. However, researchers do not know at this time whether individuals who develop acquired dystonia's have a genetic predisposition that makes them vulnerable to dystonia. It could also be that individuals who do not develop dystonia, despite injuries to the nervous system known to cause symptoms in some cases, have a protective factor that is lacking in those individuals who do develop secondary dystonia's. Moreover, dystonia can occur as a symptom of various genetically-caused diseases, in which the inheritance patterns vary.

One of the greatest mysteries that dystonia researchers are working to solve is the fact that not everyone who inherits a dystonia-causing gene will develop symptoms.

Most of the dystonias for which genes have been identified are dominantly inherited, meaning that only one parent needs to have the gene for a child to inherit the disorder. However, most dystonia genes also exhibit reduced penetrance, which means that not every person who inherits the gene will develop symptoms.

Scientists are actively seeking additional dystonia genes. Studying the genetics of dystonia will not only help refine diagnostic and reproductive health applications, but also contributes greatly to our understanding of dystonia and quest for better treatments and a cure.

Some families with specific inherited types of dystonia have used in vitro fertilization (IVF) and pre-implantation genetic testing (PGT) to essentially eliminate the risk of future generations being born with dystonia-causing gene mutations.

What is In Vitro Fertilization?
In vitro fertilization (IVF) is a method of assisted reproduction that involves combining an egg with sperm in a laboratory. If the egg fertilizes and begins cell division, the resulting embryo is transferred to the uterus where it will hopefully implant in the uterine lining and develop into a successful pregnancy.

What is Preimplantation Genetic Testing?
Preimplantation genetic testing (PGT) is a group of techniques to examine embryos during in vitro fertilization (IVF) for a range of genetic problems before possible transfer to the uterus.

These genetic defects include single gene disorders (for example, DYT1-dystonia), a missing or extra chromosome in the embryo, or the rearrangement of genes which can cause pregnancy loss and birth defects.

When PGT is used to detect single gene disorders, a child has a more than 99% chance of being born without the gene mutation for which the embryos are screened.

The first step for individuals and couples who wish to learn more about PGT is to consult a genetic counselor.

To locate a genetic counselor, consider asking your movement disorder specialist for a recommendation, consult your health insurance provider, or contact a local reproductive health clinic.

A detailed discussion of genetic dystonias is available from GeneReviews.

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