What is NMO?
Neuromyelitis optica spectrum disorder (NMO) is a rare inflammatory disease of the central nervous system (eye nerves, spinal cord, and brain).1
NMO is an autoimmune disease. This means that the immune system cannot tell the difference between healthy cells and invaders like viruses, fungi, or bacteria. Because it cannot tell the difference, the body begins to attack and damage healthy cells.1
NMO is also a chronic disease. This means that it lasts for a long time or never completely goes away.1
What are the causes?
Antibodies are proteins your immune system makes to kill germs. In autoimmune diseases, antibodies can also be harmful. The harmful antibody in NMO targets a protein called aquaporin-4 (AQP4).2,3
AQP4 is found on brain cells called astrocytes and helps control water balance in the brain. The brain, spinal cord, and eye nerve (optic nerve) have AQP4. AQP4 antibodies (AQP4-IgG) damage the protective coating (myelin) of the brain cells, producing more proteins that lead to inflammation.3
While many with NMO test positive for AQP4 antibodies (AQP4-IgG), about 1 in 4 do not. Some have no antibodies at all. This adds to the mystery behind the cause of the disease.4
Antibodies targeting another protein called myelin oligodendrocyte glycoprotein (MOG) can also be present in NMO. They are believed to cause similar optic nerve or spinal cord attacks in MOG antibody NMO (also called MOG-IgG NMO). However, symptoms of this condition develop differently and need to be treated differently from those of AQP4 antibody NMO (AQP4-IgG NMO). Men and women are equally likely to get MOG antibody NMO. Children have this disease more often than they have AQP4 antibody NMO (AQP4-IgG NMO).2,3,5-8
It is possible that MOG antibody NMO (MOG-IgG NMO) and AQP4 antibody NMO (AQP4-IgG NMO) will eventually be considered separate diseases, though this is debated. For now, MOG antibody disease (MOG-IgG NMO) and AQP4 antibody disease (AQP4-IgG NMO) are considered subtypes of NMO.5,6
What are the symptoms?
The symptoms of NMO can be different depending on which parts of the brain and spine are affected. Symptoms also vary in severity and how long they last. Common symptoms include:9
- Blurry vision or blindness
- Weakness or paralysis in arms or legs
- Painful muscle spasms
- Numbness or a loss of sensation in areas of the body
- Nausea, vomiting, and/or persistent hiccups
- Problems with the bladder or bowels
- Sleeping problems
Who gets NMO?
The reported number of people who have NMO varies based on gender and ethnicity. The disease affects about 1 to 10 people per 100,000 worldwide. Although NMO is found everywhere, some locations have higher rates of disease. This is due to higher numbers of some racial groups in those locations, though the link between NMO and race is not known. Higher rates of NMO have been found in people of African or Asian descent.1
Women are diagnosed with NMO 9 times more often than men are. Doctors think women get NMO more than men do because of hormone changes over time, including hormone changes with pregnancy. NMO can occur at any age, but the average age of onset is between age 40 and 50. Fewer than 5 percent of those with NMO are under the age of 18.2,7,9,10
What is an antibody test?
Your doctor might test your blood for the AQP4 antibody (AQP4-IgG) or MOG antibodies (MOG-IgG). These tests help doctors distinguish NMO from multiple sclerosis (MS) and other brain or nerve conditions. Those who initially test negative for antibodies are often re-tested later if doctors suspect NMO.11
How is it treated?
If you are currently experiencing an attack of NMO, your doctor will prescribe short-term (acute) treatments. Acute treatments may include:12
- Steroids – These potent anti-inflammatory drugs decrease inflammation.
- Plasma exchange – Also known as plasmapheresis, this procedure removes the harmful substances in your blood that are attacking your brain, spine, and eye nerves. The substance is replaced with either your own cleaned plasma (a part of blood that carries antibodies) or plasma from donors.
It is important to prevent further attacks of NMO since attacks are what lead to further damage of the nervous system. To help prevent these attacks, your doctor will prescribe drugs that will suppress (turn down) your immune system. As of early 2021, the U.S. Food and Drug Administration (FDA) has approved 3 preventative drugs for those who test positive for AQP4 antibodies (AQP4-IgG):13
Can my children get it?
NMO is not usually passed on in a family. Up to 3 out of 100 people with NMO have a family member who also has it. Doctors are still trying to figure out how genes and NMO are related. Your doctor might have you talk to a genetic counselor. This is a person who specializes in genetic testing and how genes impact disease.14
Is NMO the same as multiple sclerosis (MS)?
No. In the past, doctors thought NMO was a type of MS. We now understand that NMO is its own disease. Both NMO and MS attack the myelin, the outer protective coating on nerve cells of the brain, spine, and eye. Because of this, both diseases share similarities that can make diagnosis a challenge. For example, both diseases can cause extreme fatigue, muscle weakness, spasticity (muscle stiffness and tightening), and swelling of the nerves in the eye (optic neuritis).1
However, there are major differences between the conditions. Many of those with NMO have AQP4 antibodies (AQP4-IgG) in their blood. This is not found in those with MS. Also, the patterns of attacks, the areas of the brain that are damaged, and the severity of pain and fatigue are different in each disease. Your doctor will be able to help you get the diagnosis you need. You may need to see multiple doctors in order to get a diagnosis of NMO.15
Is my immune system not working well if I have NMO?
No. Having an autoimmune disease does not mean your immune system is broken. Your immune system is one of the most complex systems in your body. It is powerful, and yet, much remains unknown about its workings. Extensive research is being done to figure out the ins and outs of NMO. The ultimate goal is to prevent the autoimmune attack of healthy tissues, solve the mystery, and cure the disease.16
Is there a cure?
There is not a cure for NMO at this time. Advances in medicine happen quickly, and there is hope that more treatment will be on the horizon. Rare diseases like NMO need more people to enroll in clinical trials and participate in research as it becomes available.1