Neuromyelitis optica spectrum disorder (NMOSD) is a rare condition that’s distinct from multiple sclerosis (MS), but the two conditions share some similarities. Commonly called neuromyelitis optica and formerly known as Devic’s disease, NMOSD can sometimes be misdiagnosed as MS.

Understanding the basics of NMOSD may help those living with the condition better navigate potential symptoms, diagnosis, and treatment options. Here, we’ll cover eight key facts to help you understand this rare condition.

1. NMOSD Is a Rare Disease

NMOSD is much less common than MS. It affects about 1 to 10 people per 100,000 worldwide. That’s about 15,000 people in the United States. Unlike MS, which affects millions, NMOSD is considered a rare disease.

NMOSD most commonly starts with a sudden, severe attack when someone is in their 30s or 40s.

2. Attacks Often Start Suddenly

NMOSD typically begins with a sudden, usually severe attack. The condition most often appears in adults in their 30s and 40s, but it can happen at any age.

The first signs of NMOSD are often optic neuritis (painful loss of vision) or transverse myelitis (inflammation of the spinal cord that can cause weakness, numbness, or lack of bladder control). These attacks are typically much more severe than MS relapses (temporary flare-ups of symptoms) and can lead to permanent damage if not treated quickly.

3. Symptoms Can Be Severe

NMOSD tends to affect the optic nerve and spinal cord, but it can also involve other areas of the brain. Signs and symptoms may include:

• Vision loss or eye pain in one or both eyes
• Weakness or paralysis in the arms or legs
• Painful muscle spasms
• Numbness or tingling
• Difficulty walking
• Loss of bladder or bowel control
• Sleeping problems

Persistent nausea, vomiting, or hiccups can happen when the brainstem is involved. In severe cases, people may experience confusion or have trouble breathing or swallowing. Untreated attacks can lead to permanent blindness, paralysis, or other serious complications. That’s why it’s so important to recognize NMOSD, start treatment early, and manage symptoms.

4. Relapses Commonly Occur

NMOSD has a relapsing-remitting pattern, with severe attacks followed by periods of recovery. Without treatment, about 90 percent of people with NMOSD will have a relapse within five years of their first episode. Approximately 50 percent will experience their first relapse within a year.

Unlike MS, NMOSD usually doesn't have a progressive form, in which symptoms gradually worsen over time. However, each NMOSD relapse can cause more damage, so preventing relapses is key.

5. NMOSD Is an Autoimmune Disease

NMOSD is an autoimmune disease in which the immune system mistakenly attacks the central nervous system (CNS). Most people with NMOSD are seropositive, meaning they have antibodies (immune proteins) that target aquaporin 4 (AQP4). AQP4 is a protein that plays a key role in water transport across cell membranes in brain and spinal cord cells.

Women, people of certain ethnic backgrounds, and those with a family history of autoimmune disease have a higher risk of developing NMOSD.

6. Certain Factors Raise the Risk of NMOSD

Scientists don’t know exactly what causes NMOSD, but they’ve identified some risk factors. These include:

• Being female — More than 80 percent of people with NMOSD are women, according to the National Multiple Sclerosis Society.
• Being of African or Eastern Asian descent — NMOSD is more common in these populations, per the National Multiple Sclerosis Society.
• Having a personal or family history of other autoimmune disorders

Only about 3 percent of people with NMOSD have another relative with the disease. However, about half of people with NMOSD have a personal history or a family member with another type of autoimmune disease, like lupus or Sjögren’s syndrome.

Having these risk factors doesn’t mean someone will definitely develop NMOSD, but they may increase the chances. Recognizing these factors can help healthcare providers identify people at higher risk and order testing quickly if symptoms occur.

7. Medications Can Help Prevent Relapses

Although there’s no cure for NMOSD, current treatment options can help manage symptoms and prevent relapses. Treatment typically focuses on two main goals — stopping acute (sudden, severe) attacks and reducing the risk of future ones.

During acute attacks, high-dose corticosteroids like methylprednisolone are commonly used to reduce inflammation and are typically the first-line treatment. For people who don’t respond well to steroids, plasma exchange, also known as plasmapheresis, may be an option. This procedure, similar to a blood transfusion, involves removing blood from the body, filtering out the harmful proteins linked to NMOSD attacks, and then returning the blood to the body.

To prevent relapses, long-term therapies include immunosuppressant medications. Several treatments are available for reducing the risk of relapses. These medications include traditional immunosuppressants (such as azathioprine and mycophenolate), rituximab, and tocilizumab, as well as drugs approved by the U.S. Food and Drug Administration (FDA) for treating seropositive NMOSD. These FDA-approved drugs include:

• Eculizumab (Soliris)
• Inebilizumab-cdon (Uplizna)
• Satralizumab-mwge (Enspryng)
• Ravulizumab (Ultomiris)

Read more about treatment options for NMO.

It’s important to know that some disease-modifying therapies (DMTs) for MS can actually make NMOSD worse. Some of these DMTs include interferon beta medications (such as Avonex and Extavia), natalizumab (Tysabri), and fingolimod (Gilenya). This is why it’s vital to ensure you have the correct diagnosis before making treatment decisions.

8. Proper Treatment Means a Promising Outlook

NMOSD is a lifelong condition, but with the right treatment, many people can lead full and active lives. Early diagnosis and timely treatment are essential to improving outcomes and reducing the risk of long-term disabilities such as blindness or paralysis.

With proper treatment, people with NMOSD have a life expectancy close to normal. Read more about prognosis (outlook) and life expectancy with neuromyelitis optica spectrum disorder.

Talk With Others Who Understand

MyMSTeam is the social network for people with MS and their loved ones. On MyMSTeam, more than 164,000 members come together to ask questions, give advice, and share their stories with others who understand life with MS.

Are you living with neuromyelitis optica spectrum disorder or MS? Did your neurologist discuss both conditions during your diagnosis? Share your experience in the comments below, or start a conversation by posting on your Activities page.