Rare Disease Report

First Genetic Mutation Linked to Neuromyelitis Optica Discovered

JULY 20, 2018
Einav Keet
Researchers have identified a gene mutation linked to neuromyelitis optica (NMO), a rare brain disease that can lead to blindness and paralysis.

The National Institute of Neurological Disorders and Stroke (NINDS)—part of the National Institutes of Health (NIH)—defines NMO as an autoimmune disease of the central nervous system, which mainly impacts the optic nerves and spinal cord. As with other autoimmune diseases, NMO causes the immune system to turn its defenses on healthy cells, attacking them. Patients with NMO can experience optic neuritis, leading to eye pain and vision loss. In addition, transverse myelitis—inflammation of the spinal cord—often occurs in those with NMO and is known to lead to numbness, weakness or paralysis of arms and legs, and loss of bladder and bowel control. There is currently no cure for NMO and no therapy approved by the US Food and Drug Administration (FDA), though corticosteroids and immunosuppressive drugs can help to treat and prevent attacks.

Now, a new study published in the journal Nature Communications details recent findings from a multi-institutional team of researchers who say they’ve discovered a gene mutation associated with NMO. In the study—which included researchers from Biogen Inc., Harvard Medical School, the Massachusetts Institute of Technology, Broad Institute, and University of Texas Southwestern Medical Center—the research team conducted DNA analysis on a total of 215 NMO cases and 1,244 controls. Prior to this study, researchers had not identified any genes associated with NMO, though cases of family members sharing the condition hinted at inheritance and genetic factors.

The study team found that a variation in a complement component gene was associated with an increased risk of developing NMO. This gene produces a protein that typically harms bacteria by binding to antibodies and damaging whatever it is attached to. In those with NMO, the antibodies instead target the nervous system. The researchers say they hope that their findings will help them understand why some patients benefit from treatment and have their condition go into remission, while drugs prove ineffective for other patients.  

“This outcome shows that doing in-depth research pays off, and more studies like this may be needed to find the problem behind other rare conditions,” said Benjamin Greenberg, MD, one of the study’s authors and a researcher with UT Southwestern’s Peter O’Donnell Jr. Brain Institute, in a recent statement. “By taking a rare disease and doing more than just reading every third or fourth page of genetic code, we have modeled NMO in a much more accurate way.”

In a study published in early 2018, researchers in Japan reported promising findings on the use of an antibody to alleviate NMO symptoms in rats. Dr Greenberg notes that the rarity of NMO has not helped to draw more research into possible causes of the disease and potential treatments. “To target a disease as rare as this, to put this much technology behind trying to understand the disease—it hasn’t been done before,” he said. “This study has given insights into this condition that aren’t just new but are distinctly different from other studies.”

Approximately 1 to 2 individuals per 100,000 are affected by NMO worldwide, and with an estimated 200,000 to 3 million cases worldwide, the condition is more likely to affect women.

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