If you have been diagnosed with neuromyelitis optica spectrum disorder (NMOSD or NMO), you may have also been diagnosed or have been living with another autoimmune condition. The symptoms of NMO may overlap with other conditions. This complicates things for both you and your doctor. Understanding which diseases may coexist with NMO is helpful to better understanding NMO.
What is an autoimmune condition?
Autoimmune means that your 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
Why are other autoimmune conditions linked to NMO?
Doctors do not know the exact reason why some conditions can coexist with NMO. Coexisting conditions are known as comorbidities. The term comorbidity is used to describe a condition or illness that occurs at the same time of another condition or illness. Comorbid illnesses can interact in ways that worsen both. Morbidity should not be confused with the term mortality. Morbidity means disease or illness, and mortality means death.2
Which conditions are most common?
NMO has been linked to other autoimmune diseases. The most common include:
Lupus
Lupus is a chronic autoimmune disease. In lupus, the immune system attacks healthy tissue, such as the skin, joints, kidneys, brain, and other organs. The symptoms and severity of the disease can vary widely between people.3
When most people talk about “lupus,” they mean systemic lupus erythematosus (SLE), since it is the most common of the 4 types of lupus. It accounts for about 70 percent of people diagnosed with lupus.3
Spine MRI findings may be similar in both NMO and lupus, which makes it challenging for doctors to get the right diagnosis. Treatment differs for both lupus and NMO, so getting the right diagnosis is important for outcomes of NMO.4
Sjögren’s syndrome
Sjögren’s (“SHOW-grens”) syndrome is an autoimmune disorder where the body attacks its own glands that make tears and saliva.5
In one study, Sjögren’s syndrome was present in about 8 percent of those with NMO, while Sjögren’s syndrome occurred in fewer than 1 percent of those without NMO. The link between these diseases is not well understood. The antibodies that cause damage in both diseases may be a reason these 2 diseases can coexist.6
Autoimmune thyroid disease
Autoimmune thyroid disease is also known as Hashimoto’s disease. In this disease, harmful antibodies attack the thyroid gland, leading to decreased function (hypothyroidism).7
In one study, those with highly active NMO were 5 times more likely to have autoimmune thyroid disease than those without NMO. Doctors think that harmful antibodies in NMO and autoimmune thyroid disorder may be the link to both of these diseases.6
Myasthenia gravis
Myasthenia gravis (my-us-THEE-nee-uh GRA-vis) is a chronic autoimmune disease where the body attacks areas where nerves communicate with muscles. This communication is what makes muscles work. Without the ability to properly communicate, the muscles become weak and tire easily. Both NMO and myasthenia gravis (MG) can coexist. Doctors think they may coexist since both NMO and MG occur because of antibodies and have similar inflammation in the body.8,9
Some autoimmune diseases may mimic NMO. These diseases do not coexist with NMO but can complicate your path to diagnosis. A full history of your symptoms, detailed physical exam, and different tests can help your doctor decide which disease or condition is most likely.