People living with multiple sclerosis (MS) are at a higher risk of developing other health conditions than the general population. Among these potential comorbidities (co-occurring health conditions) is rheumatoid arthritis (RA), a disease in which the autoimmune system attacks the joints. A 2016 study found that people with MS had a 70 percent higher incidence of RA than the general population.

More than 600 MyMSTeam members report that they’re living with both conditions, and some have described their experiences. “I was diagnosed with RRMS [relapsing-remitting MS] in 2008, then rheumatoid arthritis in 2013,” one member shared. “I manage both diseases through exercise and diet in conjunction with DMDs [disease-modifying drugs].”

Another member said, “I have rheumatoid arthritis along with MS. Mornings are hard. I do stretching in the morning. It helps.”

Knowing some of the similarities and differences between RA and MS may help you and your doctor determine a potential cause of new symptoms, such as joint pain you haven’t experienced before. It can also be useful to understand what these autoimmune conditions have in common and how similar treatments may help with reducing inflammation and suppressing the immune system.

4 Similarities Between MS and Rheumatoid Arthritis

MS and RA have a number of characteristics, including how the symptoms, treatment options, and mechanisms of both diseases are similar. Here are some similarities between the two conditions.

1. MS and Rheumatoid Arthritis Are Both Autoimmune Diseases

MS and RA are both classified as autoimmune diseases. In autoimmune disorders, the immune system attacks healthy tissue and can cause a range of symptoms throughout the body that are sometimes difficult to diagnose.

Risk factors for immunological diseases include family history, environmental factors, and lifestyle factors. Autoimmune diseases such as MS and RA have been linked to vitamin D deficiency, and some research has shown that vitamin D supplementation may reduce the risk of autoimmune disorders. However, before starting any type of dietary supplement, it’s important to speak with your health care provider. Some supplements can cause unwanted side effects.

2. Both MS and Rheumatoid Arthritis Are Progressive and Can Cause Disability

As progressive diseases, both MS and RA can lead to some form of disability. In a 2013 study of more than 27,000 people with MS, approximately 50 percent reported that disability interferes with daily activities 15 years after diagnosis. The prevalence of disability rises over time as the MS disease activity progresses.

There is also a high incidence of disability in people with RA, and some research indicates that it occurs at more than twice the rate of the general population.

3. MS and Rheumatoid Arthritis Can Have Similar Symptoms

Some symptoms are common among various autoimmune diseases. Joint pain, major depressive disorder (MDD) — also known as clinical depression — and fatigue are some of the symptoms that MS and RA share, and they can interfere with a person’s quality of life.

Joint Pain

RA is commonly associated with joint pain and stiffness caused by inflammation and damage to the lining of the joints. However, people with MS can also experience joint pain caused by spasticity (muscle stiffness or tightness) and mobility problems, which can put added stress on joints.

Depression

People with MS have an increased risk of major depression, defined as having one or more episodes of intense psychological depression or loss of interest or pleasure that lasts two or more weeks.

Some research indicates that depression rates may be more than twice as high among people with MS than the general population. Depression in MS is linked to the emotional stress and loss of function that come with disease progression. Research also indicates that depression in MS may be associated with demyelination — damage to the myelin sheath (protective tissue) around nerves — that can occur in the brain.

As with MS, depression in RA can occur due to the burden of the disease and symptoms that affect physical well-being and functioning. Researchers have also linked depression to chronic inflammation from RA.

Fatigue

Fatigue is one of the most common symptoms of both MS and RA. About 80 percent of people with MS report experiencing fatigue. Although scientists don’t fully understand the exact cause of fatigue in MS, they believe it’s partly related to sleep loss from symptoms such as muscle spasms, bladder dysfunction, and mood disorders.

Fatigue is also a common symptom in people with RA. Like MS, RA can lead to fatigue that often occurs with other symptoms such as pain, sleep disturbance, and depression.

4. MS and Rheumatoid Arthritis Share Treatment Options, Including Biologics and Corticosteroids

Although there’s no known cure for either MS or RA, both conditions can often be managed with biologic medications. Certain biologics are used as disease-modifying therapy (DMT) for MS, while others are used as disease-modifying antirheumatic drugs (DMARDs) for RA. They’re taken by subcutaneous (under the skin) injection or intravenous (into a vein) infusion, not in pill form because they consist of large molecule proteins that the digestive system can’t properly absorb.

Biologic drugs are derived from animal and human cells. This type of drug targets and inhibits overactive proinflammatory proteins in the immune system with drugs such as tumor necrosis factor (TNF) inhibitors. Most biologic drugs that treat MS and RA are a type of monoclonal antibody, which accounts for the “-mab” at the end of many biologic drug names. Rituximab (Rituxan) is the only biologic indicated for treating RA that’s also sometimes prescribed for MS.

Other common treatments for both conditions include corticosteroids and physical therapy.

4 Differences Between MS and Rheumatoid Arthritis

Though MS and RA have similarities, they’re distinct health conditions with many notable differences.

1. MS and Rheumatoid Arthritis Attack Different Tissues

MS is a disease of the central nervous system (CNS), caused by the autoimmune system damaging nerve fibers in the spinal cord and brain. This can result in a number of painful and disabling symptoms throughout the body, such as mobility difficulties, vision problems, and bladder and sexual dysfunction.

In rheumatoid arthritis, on the other hand, the autoimmune system attacks the linings of joints. Joint damage caused by the resulting inflammation can be severe, sometimes even requiring joint replacement surgery. Inflammation from RA can also affect the lungs, heart, blood vessels, eyes, skin, and other parts of the body. Although inflammation from RA may affect nerve tissues, the disease does not specifically attack nerves.

2. Different Sources Cause Pain in MS and Rheumatoid Arthritis

As many as 75 percent of people with MS report that they experience pain, according to a 2013 study in Current Neurology and Neuroscience Reports. Much of the pain from MS is characterized as central pain — pain caused by damage to or dysfunction of the central nervous system. The damage interferes with the nerves’ ability to transmit signals to the brain. This short-circuiting results in burning, stabbing, pins-and-needles, or squeezing sensations.

Other MS symptoms, such as muscle spasticity, can also cause pain. Muscle spasms can occur in the upper or lower body and cause muscles to painfully tighten and cramp.

Pain in rheumatoid arthritis is caused by synovitis, inflammation in the synovial lining of joints. The synovial lining is a thin layer of tissue that protects joints by producing lubricating and nourishing fluid for proper joint function. Joint damage in RA can cause pain in hands, fingers, wrists, knees, and other joints, which may also become swollen and red or discolored, depending on skin color.

3. Cognitive Problems Are More Acute in MS

Cognitive changes occur in about 40 percent to 65 percent of people with MS, per a 2010 study in Neurological Sciences. They’re caused by brain lesions and loss of brain tissue.

Cognitive impairment in MS may include:

• Memory problems
• Difficulty in concentrating or processing information
• Trouble with problem-solving and complex functions
• Difficulties with speaking
• Issues with visual-spatial functioning, such as depth perception or directions

Cognitive impairment may worsen with disease progression.

Rheumatoid arthritis can also cause cognitive problems. However, research indicates that cognitive impairment from RA is primarily due to chronic pain, which commonly worsens fatigue, depression, and anxiety. Pain can cause psychological distress and interfere with a person’s attention and mental functioning.

4. Different Types of Doctors Treat MS and Rheumatoid Arthritis

People with MS are treated by neurologists, doctors who specialize in neurology — that is, diagnosing and treating disorders in the brain and nervous system. Neurologists are trained to evaluate brain and nerve function based on tests such as MRI, lumbar puncture — also known as spinal tap — and evoked potential testing. These tests can help determine an MS diagnosis.

Rheumatoid arthritis is treated by rheumatologists, who are experts in bones, joints, muscles, ligaments, and tendons — all part of the body’s musculoskeletal system. In the past, doctors used the term “rheumatism” to describe when these areas of the body were swollen, stiff, or painful.

Rheumatologists treat a variety of diseases known as systemic autoimmune diseases, connective tissue diseases, or collagen vascular diseases, including RA, systemic lupus erythematosus (also known as lupus), and fibromyalgia.

Diagnosis of RA may include rheumatology blood tests that look for rheumatoid factor proteins, antinuclear antibodies, and C-reactive protein, among other indicators of RA.

When To Talk to Your Doctor

If you’re living with MS, you’re at a higher risk of developing rheumatoid arthritis — and other conditions — than the general population. It’s therefore important to watch for any changes in your health that may point to another condition and to discuss them with your doctor.

Talk With Others Who Understand

On MyMSTeam, the social network for people with multiple sclerosis and their loved ones, more than 198,000 members come together to ask questions, give advice, and share their stories with others who understand life with multiple sclerosis.

Do you have MS and rheumatoid arthritis? Share your experiences in the comments below, or start a conversation by posting on your Activities page.