If you’re living with an autoimmune disease like myasthenia gravis (MG), you have a higher risk of developing other autoimmune disorders. About 5 percent to 10 percent of people with MG are also diagnosed with another autoimmune disease.

Lupus, also known as systemic lupus erythematosus (SLE), is an autoimmune disease that’s more common in people with MG than in the general population. Keep reading to learn more about the connection between lupus and MG.

Lupus and MG Are Autoimmune Diseases

Both lupus and MG are autoimmune diseases. In autoimmune diseases, the immune system, which normally protects the body from germs and foreign invaders, mistakenly attacks healthy tissue. This happens when the immune system makes autoantibodies, which are proteins that target the body’s tissues.

While lupus and MG affect different parts of the body, researchers have found that both conditions release similar inflammatory substances.

Lupus can cause inflammation throughout the body and affect many organ systems. In lupus, autoantibodies can attack any organ in the body, causing damage to the skin, kidneys, joints, lungs, heart, and eyes.

MG only affects the neuromuscular junction — the area where nerves and muscles communicate. In MG, the immune system creates autoantibodies that target and destroy acetylcholine receptors (AChR) at the neuromuscular junction. These receptors act as a “docking site” for a chemical called acetylcholine. When autoantibodies destroy the AChR, it becomes harder for nerves to communicate with muscles, leading to muscle weakness.

How Common Is It To Have Both Conditions?

Lupus is more common than MG. The Lupus Foundation of America estimates that about 1.5 million people in the U.S. have lupus, while about 60,000 people in the U.S. have MG. Having one autoimmune condition increases the risk of developing another.

While rare, the coexistence of lupus and MG has been reported. A 2024 study found that, in a large sample representing about one-quarter of U.S. adults, 370 people had both conditions. The study also found that people with a diagnosis of MG were about 13 times more likely to develop lupus.

Who Is More Likely To Develop Lupus and MG?

Young women are more likely to have both lupus and MG. Both lupus and MG are more common in women, especially younger women. Lupus usually develops in women aged 15 to 44, while MG is more common in women under 40.

African American women are also more likely to develop both conditions. In fact, they are two to three times more likely to develop lupus compared to white women.

MG as a Risk Factor for Lupus

In most cases, MG develops before lupus. One theory is that the immune system changes after a thymectomy (surgical removal of the thymus gland) may increase the risk of lupus.

The thymus gland is where T cells mature and develop. Problems with the thymus gland can lead to T cells that make antibodies that attack the neuromuscular junction. Removing the thymus gland can improve MG symptoms and muscle weakness.

However, having a thymectomy may also increase the risk of developing lupus. People with MG who have a thymectomy are about three times more likely to develop lupus than those who don’t have a thymectomy.

This may happen because a thymectomy can cause a loss of “central tolerance,” meaning the immune system can’t tell which cells belong to the body. The loss of central tolerance and increased production of autoantibodies can increase the risk of lupus.

B lymphocytes play a major role in lupus (SLE), while T lymphocytes are critical for MG pathogenesis. CXCL13, a protein that activates both B and T lymphocytes, may explain the coexistence of these two autoimmune diseases.

In addition to lupus, thymectomy is linked to other autoimmune conditions, including:

• Hashimoto’s disease — An autoimmune thyroid disease that causes low thyroid levels
• Antiphospholipid syndrome — A condition that causes blood clots
• Cutaneous vessel vasculitis — A condition that causes blood vessel inflammation

Lupus as a Risk Factor for MG

Lupus can also develop before MG. Like other autoimmune diseases, lupus can coexist with conditions such as MG, rheumatoid arthritis (RA), and Sjögren’s syndrome. Since lupus and MG share several risk factors, some people may develop both conditions by chance. The connection between lupus and MG may be due to similarities in the molecular structure of the parts of the immune system that can trigger these diseases.

Hydroxychloroquine (Plaquenil), a common lupus treatment, has been linked to MG. Case reports show that some people have developed MG after starting hydroxychloroquine for lupus. This may happen because hydroxychloroquine can affect the neuromuscular junction, causing myopathy (muscle disease) that looks like MG.

Other side effects of hydroxychloroquine can also look like MG, such as eye problems and muscle weakness that get worse over time. It can be hard to tell the difference between MG symptoms and the side effects of hydroxychloroquine because both often affect the muscles of the head and neck.

Symptoms of Lupus vs. MG

Lupus and MG share some symptoms, which can sometimes lead to confusion. For example, lupus can cause muscle weakness if inflammation affects the muscles (myositis), usually around the hips and shoulders. MG can cause muscle weakness affecting the head, neck, arms, hands, and legs.

Both conditions can also cause eye symptoms. In lupus, eye symptoms such as blurry vision can result from dry eye or eye inflammation. If hydroxychloroquine is used to treat lupus, it may also cause eye problems or worsen MG symptoms in people who already have MG.

In MG, symptoms such as ptosis (a droopy eyelid) or blurry vision develop due to weak eye muscles.

Lupus symptoms are often milder in people with both lupus and MG. However, MG symptoms may be more severe in people with both conditions. People with lupus and MG are also more likely to have other conditions, such as pernicious anemia (an autoimmune condition that causes low red blood cells) or chronic kidney disease.

In people who develop lupus after MG, the first symptom of lupus is often joint pain. Other common lupus symptoms may include:

• Rash
• A malar rash (butterfly-shaped rash across the face)
• Headache
• Fever
• Mouth sores
• Fatigue
• Hair loss
• Swelling

Diagnosing Lupus and MG

There isn’t a single test for lupus or MG. Testing for both conditions involves testing for antibodies that attack healthy tissues. People with lupus almost always test positive for antinuclear antibodies. Most people with MG test positive for acetylcholine receptor antibodies. People with both lupus and MG may be more likely to have acetylcholine receptor antibodies.

Additional tests can check for health problems linked to either lupus or MG, such as:

• Blood tests to check the immune system, kidneys, and liver function
• Urine tests to look for infection or kidney problems
• A biopsy (tissue sample) of any affected organs to examine under the microscope
• Imaging tests to check for thymus gland tumors (thymoma)

Treatments for Lupus vs. MG

The main goal of treatment for both lupus and MG is to suppress an overactive immune system. Corticosteroids (steroids), like prednisone, are immunosuppressant medications that are often used to treat severe symptoms of lupus or MG during a flare.

Other immunosuppressant drugs can help improve symptoms or slow disease progression. However, different immunosuppressants are commonly used for lupus and MG.

For lupus, common immunosuppressants include:

• Azathioprine (Imuran)
• Cyclophosphamide (Cytoxan)
• Methotrexate (Rheumatrex)
• Mycophenolate mofetil (CellCept)

For MG, azathioprine and mycophenolate mofetil are also commonly used. However, researchers have found that corticosteroids may not work as well for MG symptoms in people with both lupus and MG. In these cases, other MG treatments may be needed, such as:

• Immunosuppressants
• Intravenous immunoglobulin (IVIG)
• Plasmapheresis (plasma exchange)
• Targeted treatments including rituximab (Rituxan) or efgartigimod alfa-fcab (Vyvgart)

Each person with MG is different. Your healthcare team will create a treatment plan based on your symptoms and other conditions. If you’re diagnosed with lupus, your treatment plan may change.

If you notice new symptoms, it’s important to follow up with your healthcare provider right away. Early diagnosis and treatment can help prevent future health problems.

Find Your Team

On MGteam, the social network for people living with myasthenia gravis and their loved ones, more than 2,800 members come together to ask questions, give advice, and share their stories with others who understand life with myasthenia gravis.

Are you living with lupus and MG? What new symptoms did you notice? Share your experience in the comments below, or start a conversation by posting on your Activities page.