If you or a loved one has myasthenia gravis (MG), you might wonder if it’s connected to other autoimmune diseases like rheumatoid arthritis (RA). Can having one condition raise your risk of developing another? Are there shared causes?

This article explores the association between myasthenia gravis and rheumatoid arthritis. Learning more about how these conditions may be linked can help you recognize symptoms, seek the right tests, and get proper treatment.

Understanding Rheumatoid Arthritis

Rheumatoid arthritis is a chronic autoimmune disorder — a type of disease in which the body attacks its own cells and tissue by mistake. In RA, the immune system attacks the synovium (the lining of the joints), leading to inflammation that can cause joint damage over time. Common symptoms of rheumatoid arthritis include:

• Joint pain and stiffness, often starting in the hands or feet
• Swelling and warmth in the affected joints
• Muscle weakness
• Fatigue (tiredness that doesn’t go away with proper rest)
• Morning stiffness
• Weight loss and fever

Rheumatoid arthritis is considered a systemic disease, meaning it affects the entire body and can involve the lungs, heart, and blood vessels. RA affects about 0.5 percent to 2 percent of people worldwide, and it’s more common in women, people who smoke, and people with a family history of the disease, according to the journal Frontiers in Immunology.

Can You Have Both Myasthenia Gravis and Rheumatoid Arthritis?

People with myasthenia gravis have a slightly higher chance of developing other autoimmune conditions, including rheumatoid arthritis. While it’s uncommon to have both MG and RA, it does happen. Studies suggest that between 1 percent and 4 percent of people with MG are also diagnosed with RA. While that’s a small percentage, it’s higher than that of the general population.

Risk Factors for Myasthenia Gravis and Rheumatoid Arthritis

Scientists don’t yet know exactly why some people develop both myasthenia gravis and rheumatoid arthritis, but they have a few theories. Most involve shared risk factors, including genetics, hormones, and environmental influences.

Shared Genetic Factors

One possible risk factor is genetic predisposition — small changes in certain genes that make it more likely to develop an autoimmune disease. Genes help regulate how the immune system works, including how it tells the difference between harmful germs and the body’s own healthy cells. Sometimes, changes in these genes cause the immune system to mistakenly attack healthy tissues.

People with MG and RA often share similarities in human leukocyte antigen (HLA) genes. These genes help the body recognize foreign invaders like viruses and bacteria. Certain HLA genes are commonly linked to MG, while others raise the risk of RA. Some individuals may inherit a mix of HLA genes, which increases the risk of developing both conditions.

Gender and Hormones

Autoimmune conditions such as MG and RA are more common in women than in men. This suggests that hormones, especially estrogen, may influence how the immune system behaves. Researchers believe that estrogen may affect T cells, which help control the body’s immune response. Changing estrogen levels — such as during puberty, pregnancy, and menopause — may affect how the immune system works, possibly increasing the risk of autoimmune diseases.

Environmental Factors

Certain environmental and lifestyle factors can increase the risk of autoimmune conditions. Smoking is a known risk factor for RA and may also worsen MG. Other possible triggers include infections, stress, and dietary factors, which may cause the immune system to become overactive and produce autoantibodies — proteins that mistakenly attack the body’s own tissues.

Autoimmune Pathways for Myasthenia Gravis and Rheumatoid Arthritis

Although both RA and MG involve overactive T cells and harmful autoantibodies, they affect different parts of the body. In MG, the attack happens at the place where nerves connect to muscles. In RA, the joints come under attack. In both cases, the immune system can’t tell the difference between healthy cells and real threats, leading to ongoing symptoms.

Immune Pathways in Myasthenia Gravis

In myasthenia gravis, autoantibodies target proteins called acetylcholine receptors (AChRs), which sit on the surface of cells. These receptors receive signals from nerves that tell muscles to contract. Some people with MG also have autoantibodies that attack another protein called muscle-specific kinase (MuSK), which helps organize AChRs at the neuromuscular junction.

When autoantibodies block or destroy AChRs or MuSK, nerve signals can’t reach the muscles properly. This disruption causes the muscle weakness and fatigue seen in MG.

Sometimes, a person can have myasthenia gravis even if no AChR or MuSK antibodies are found in their blood. Researchers are still working to understand other possible causes.

Immune Pathways in Rheumatoid Arthritis

In rheumatoid arthritis, the immune system mistakenly attacks the soft lining inside the joints. This process starts when two types of immune cells — T cells and B cells — become overactive. T cells release chemical messengers called cytokines, such as interleukin-6, which trigger inflammation. B cells make autoantibodies, such as rheumatoid factor, that tag healthy joint tissue by mistake. These immune signals lead to more inflammation and, over time, damage the joints and cause pain.

How Are Myasthenia Gravis and Rheumatoid Arthritis Diagnosed?

Diagnosing myasthenia gravis and rheumatoid arthritis often involves testing for specific autoantibodies linked to each condition. Because these diseases share symptoms with other conditions, getting an accurate diagnosis is essential for finding the right treatment.

Diagnosis of Myasthenia Gravis

To diagnose myasthenia gravis, your doctor will ask about your symptoms and perform a physical exam. If they suspect MG, the next step is usually a blood test. This can be done in a doctor’s office or a clinic, where a small blood sample is taken using an intravenous (IV) syringe. The blood is checked for anti-AChR or anti-MuSK antibodies. These tests are often the most reliable way to confirm MG. Other tests might include:

• Electromyography (EMG) — This test measures how well muscles respond to nerve signals and indicates how much the neuromuscular junction has been damaged.
• Computed tomography (CT) or magnetic resonance imaging (MRI) scans — These imaging tests look for changes in the thymus gland, a part of the immune system that can sometimes be enlarged or have a tumor in people with MG.

Diagnosis of Rheumatoid Arthritis

Blood tests are also commonly used to help diagnose rheumatoid arthritis. These tests check for autoantibodies such as rheumatoid factor antibodies, which are common in people with RA. Imaging tests may also be used to confirm the diagnosis or see how much damage the disease has caused. X-rays, CT scans, and MRIs can show signs of joint swelling, bone erosion, or other changes related to long-term inflammation.

Treatments for Myasthenia Gravis and Rheumatoid Arthritis

Treatments for both conditions focus on calming the immune system and managing symptoms. Although MG and RA usually affect different parts of the body, some of their treatments overlap.

Treatments for Myasthenia Gravis

MG treatments aim to improve communication between nerves and muscles while holding back the immune system attack. Medications called acetylcholinesterase inhibitors, such as pyridostigmine, help enhance the effects of acetylcholine and improve muscle strength.

Doctors often prescribe corticosteroids, such as prednisone, to reduce inflammation and calm the immune response. For people who need stronger or longer-term treatment, other immunosuppressants may be added. These include older drugs like azathioprine and mycophenolate mofetil, as well as monoclonal antibodies, which help lower immune activity.

In some cases, procedures such as plasmapheresis (plasma exchange) or intravenous immunoglobulin (IVIG) may be used to quickly remove harmful autoantibodies from the blood and relieve symptoms. Newer treatments like efgartigimod alfa-fcab and ravulizumab-cwvz can also help by lowering autoantibody levels and reducing their harmful effects.

Treatments for Rheumatoid Arthritis

The main goal of RA treatment is to control joint inflammation, relieve symptoms, and prevent long-term damage. Early treatment might involve nonsteroidal anti-inflammatory drugs (NSAIDs) to help reduce pain and swelling. Corticosteroids may also be used to manage flares (periods of worsening symptoms) and reduce inflammation.

To slow disease progression, doctors may prescribe disease-modifying antirheumatic drugs (DMARDs) to reduce the immune system attack and protect the joints. Common DMARDs include methotrexate and sulfasalazine. Doctors may also use newer medications called Janus kinase (JAK) inhibitors, such as baricitinib, tofacitinib, and upadacitinib. JAK inhibitors help control inflammation and protect the joints.

In more advanced cases, biologic agents may be added to target specific parts of the immune system responsible for the inflammatory response in RA. These drugs include rituximab and infliximab, which can help reduce symptoms and protect the joints.

Work With Your Healthcare Team

Although myasthenia gravis and rheumatoid arthritis are both autoimmune diseases, they affect the body in different ways and require different treatments. Understanding how they’re similar — and how they’re not — can help you talk with your doctor, recognize symptoms early, and get the right tests and care.

Talk With Others Who Understand

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

Are you living with myasthenia gravis or rheumatoid arthritis? What helped you get your diagnosis or find the right treatment plan? Share your experience in the comments below, or start a conversation by posting on your Activities page.