Rare Gene Mutation Linked with High MS Risk
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People with a rare genetic mutation are very likely to develop a severe form of multiple sclerosis (MS), a new study finds.

The findings mark the first time researchers have discovered a genetic mutation that is so strongly tied to the chronic, nerve-damaging disease. In the study, people with a particular mutation in a gene called NR1H3 had a 70 percent chance of developing a rapidly progressing form of MS.

This genetic mutation is not common — it appears in only about 1 in every 1,000 MS patients, the researchers said. Still, the results will help researchers better understand this form of MS, and could even help in the search for new treatments for the disease, the researchers said. In addition, people with a family history of MS could be screened for this mutation, which could aid in early diagnosis and treatment, the researchers said.

"If you have this gene, chances are you will develop MS and rapidly deteriorate," Dr. Anthony Traboulsee, a co-author of the new study and an associate neurology professor at the University of British Columbia in Vancouver, said in a statement. "This could give us a critical early window of opportunity to throw everything at the disease, to try to stop it or slow it. Until now, we didn't have much basis for doing that." [7 Diseases You Can Learn About From a Genetic Test]

MS is a disease of the nervous system, in which the body's immune system attacks the protective covering of nerve cells called myelin. This attack causes damage that impairs or blocks communication between the brain and the body, and leads to symptoms such as muscle weakness, vision problems, trouble with balance and coordination, and thinking and memory problems, according to the National Institutes of Health.

Most people with the disease have a form called "relapsing-remitting MS," meaning they have sudden symptoms, but then experience periods of remission or even complete recovery from their symptoms. However, about 10 to 15 percent of MS patients have "primary progressive MS," in which patients' symptoms continue to get worse over time.

Although researchers knew that MS can run in families, earlier studies hadn't found any genes that strongly increased the risk of MS.

In the new study, researchers analyzed genetic information from a family in Canada that had five members with primary progressive MS in two generations. The researchers were able to find a single mutation in the gene NR1H3 that was present in all the family members with the disease. They then turned to a database of more than 2,000 MS patients, and found the same mutation in another family that also had several family members with MS.

In total, they identified seven people with the mutation who had primary progressive MS.

However, they also found a few people with the mutation who didn't have MS, which shows that having this mutation does not destine someone to develop the disease. This means that some other genetic or environmental factors may be necessary to trigger the disease, the researchers said.

Previously, the researchers found other genetic markers within NR1H3 that also slightly increased people's risk of developing primary progressive MS. So even if patients don't have the rare mutation strongly linked with MS that was uncovered in the new study, they might still benefit from future treatments that target the NR1H3 gene, the researchers said.

The new finding will also allow researchers to develop a better animal model of MS, they said. Until now, researchers have simulated MS in mice in indirect ways, such as by giving them a drug that damages myelin, but this doesn't mimic how the disease begins in people. Now, researchers can genetically engineer mice that have the mutation discovered in the study, which will allow them to better understand how this form of the disease develops, the researchers said.

The study is published today (June 1) in the journal Neuron.

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