Why Fibromyalgia and Rheumatoid Arthritis Commonly Occur Together

Rheumatoid arthritis (RA) and fibromyalgia (FMS) are chronic pain conditions that commonly co-occur. RA is an autoimmune disease in which your immune system attacks your joints. FMS is primarily thought of as a neurological condition in which pain signals are amplified, though research suggests that some cases may involve autoimmunity.

These conditions have many of the same symptoms and are believed to have some shared underpinnings as well. Pain and fatigue are primary symptoms of both RA and FMS, which can make it hard for doctors to tell them apart. When you have both, diagnosis becomes even harder.

Following through with that process is essential, though, as treatments for RA are not the same as those for fibromyalgia.

How They're Linked

Researchers don't know the precise cause(s) of either condition or why fibromyalgia and rheumatoid arthritis are seen together in patients so often, but some theories have emerged.

One thing that's become clear is that these illnesses have a substantial overlap in risk factors and causal factors.

Age and Sex

Most cases of RA are diagnosed in people between the ages of 40 and 60. FMS skews younger, developing most often between ages 20 and 50.

Women develop these conditions more than men, accounting for about 75% of RA diagnoses and between 75% and 90% of FMS diagnoses.

Sex hormones, especially estrogen, and hormonal events such as pregnancy and menopause are believed to play a role in the development of both conditions.

Genetics

Both conditions have a tendency to "cluster" in families, suggesting a genetic predisposition.

Some specific genes have been identified as potential causal factors; notably, genes for a part of the immune system called the human leukocyte antigen (HLA) complex may play a role in both RA and FMS. The specific HLA genes may not be the same in both conditions, though.

Infectious Agents

Exposure to certain viruses and bacteria are suspected to alter some people's immune systems and trigger autoimmunity (as in RA) or other types of immune dysfunction (such as those seen in FMS). Both conditions are tentatively linked to several different infectious agents.

Research from 2018 showed that the Epstein-Barr virus (EBV), which causes mononucleosis (mono), is linked to RA and numerous other autoimmune diseases. FMS research suggests a possible link to EBV as well.

Lifestyle

Two major lifestyle factors have been associated with an elevated risk of both fibromyalgia and RA: 

• Smoking cigarettes
• Higher body weight

They're connected to more severe symptoms in both cases, as well.

Which Comes First?

While the list of causes and risk factors seems to paint a picture of two diseases with a common starting point, if that were the whole picture, you could assume that people with FMS would develop RA at about the same rate as those with RA develop FMS. This is not the case.

Studies show that people with RA are more likely to develop FMS, but people with FMS are no more likely than anyone else to develop RA.

In fact, it appears that people with a wide array of chronic-pain conditions develop FMS at a high rate, including not only RA but osteoarthritis, systemic lupus erythematosus, and ankylosing spondylitis. Some scientists believe that's because chronic pain can cause changes in the way the nervous system perceives and processes pain, and that that process can trigger FMS.

This idea is supported by a study published in Arthritis Care & Research, which demonstrates how people with RA can develop high levels of pain sensitization (an exaggerated physical response to pain)—a known feature of FMS.

Not everyone with chronic pain will develop FMS, though. The common causes and risk factors, therefore, probably play a role.

Symptoms

While symptoms of RA and symptoms of FMS can be extremely similar, each has additional symptoms that aren't seen in the other.

For instance, "fibromyalgia is not associated with joint swelling, which commonly occurs with rheumatoid arthritis, although fibromyalgia patients often complain that their joints 'feel' swollen," says Scott J. Zashin, MD, clinical assistant professor at University of Texas Southwestern Medical School, Division of Rheumatology, in Dallas, Texas. 

Cognitive dysfunction—including problems with short-term memory, multi-tasking, communication, and spatial awareness—is so characteristic of FMS that it has been nicknamed "fibro fog." But this is not a symptom of RA.

Even when a symptom is associated with both conditions, though, they can present with notable differences.

Consider differences in pain:

• RA can impact any joint and even your organs, but it most often involves the small joints of the hands and feet.
• FMS pain can strike anywhere, but it's widespread by definition and more common along the spine than in the extremities.

"The complaint of widespread body pain associated with typical fibromyalgia tender points would also be consistent with fibromyalgia and not rheumatoid arthritis," he says.

Fatigue is another example of how a shared RA and fibromyalgia symptom can differ:

• Rest and sleep may improve RA-related fatigue.
• On the other hand, with fibromyalgia, fatigue often persists despite rest and sleep.

Compounding Effects

The pain of RA can trigger FMS flares and make your symptoms harder to control. Likewise, FMS amplifies the pain of RA—a condition called hyperalgesia.

A 2017 study shows that FMS has a major impact on the quality of life for people who also have RA. That finding is backed by another study published the same year which found that FMS had a bigger impact on people with RA's overall well-being than any other factor the study looked at.

If you're only diagnosed with one of these conditions, be sure to bring up the possibility of the other if:

• You have symptoms that are unique to the other condition
• You experience changes in the nature of your symptoms
• You see an increase in symptoms shared by these conditions

Impact and Progression

These two conditions have some striking differences when it comes to what's going on in your body and how they progress.

The pain of FMS is neurological. It's felt in the muscles and connective tissues but comes from the nervous system. Meanwhile, the pain of RA comes from joint inflammation and damage caused by the immune system's attack on the joint lining (synovium).

Perhaps the most notable difference is that RA causes damage and deformity in your joints. FMS is not linked to any joint damage, deformity, or deterioration.

The Disease Course

The course of RA is unpredictable, but most cases are progressive. After many years (or without treatment), some people with RA develop painful and debilitating deformities to the hands and feet. The larger joints, such as the hips and knees, can become severely impacted, making walking difficult or impossible.

It's common for people to believe that someone with RA will always end up in a wheelchair, but this is a myth. With proper treatment, that's far rarer than you might expect. Even so, RA can cause structural damage that imposes limits on movement and mobility. Fatigue is generally higher than in the general population.

FMS is also unpredictable. Research suggests that nearly half of people with the condition will make a significant improvement over a three-year period, and about two-thirds will improve over a 10-year period. So far, researchers don't know what factors influence the course of the illness.

FMS is debilitating in different ways than RA. Whereas someone with RA may limp due to pain in their joints after walking a long way, a person with FMS is more likely to be disproportionately exhausted, experience pain throughout their body, and have other symptoms intensify. It will also take them a significant amount of time and rest in order to recover.

Flares and Remissions

Some cases of RA have prolonged remissions in which symptoms vanish for several years. Others have periodic flares (when symptoms are more severe) and remissions (periods of lighter symptoms). The majority, however, have a chronic, progressive form of RA.

FMS typically involves flares and remissions as well, but a small minority of cases involve more or less consistent symptom levels. Long-term remissions are rare but possible.

Getting a Diagnosis

When you go to the doctor with pain that could be due to rheumatoid arthritis, fibromyalgia, or something with a similar presentation, your doctor will likely start by listening to your symptoms, asking about your medical and family history, and performing a physical exam.

No single blood test can diagnose either condition, so doctors look at multiple test results to get the total picture of what's going on. They'll likely order several tests to look for markers of inflammation in your blood, such as:

• Complete blood count (CBC)
• Erythrocyte sedimentation rate (ESR or sed rate)
• C-reactive protein (CRP)

Know, though, that even with testing, nailing down a diagnosis can take some time.

High Inflammatory Markers

FMS doesn't involve high levels of inflammation. RA does, so high levels of inflammatory markers in your blood are a good indication that you have something inflammatory and possibly autoimmune.

From there, your doctor may order blood tests for specific autoantibodies depending on which conditions they believe are likely. Antibodies for RA include:

• Anti-cyclic citrullination peptide (anti-CCP): This autoantibody is found almost exclusively in people with RA and is present in between 60% and 80% of cases.
• Rheumatoid factor (RF): This antibody is indicative of RA and is found in about 70% to 80% of people who have it.

Your doctor may also order several other blood tests, imaging tests such as X-rays and magnetic resonance imaging (MRI) to confirm the diagnosis and get an idea of how the disease may progress.

Lower Inflammatory Markers

If inflammatory markers are just slightly elevated or in the normal range, it can help point to an FMS diagnosis, which is a diagnosis of exclusion. Depending on your symptoms, your doctor may order more blood tests or imaging to rule things out.

RA is a common one to exclude because it's something doctors can diagnose with a lot more certainty. Other possible tests may be ordered for other forms of arthritis, lupus, or multiple sclerosis.

Once other possible causes of your symptoms are eliminated, your doctor can confirm an FMS diagnosis in two ways: by conducting a tender-point exam or based on scores on a specially designed evaluation.

Treatment Recommendations

Though there is symptom overlap between RA and FMS, treatment is not the same. To be effective, treatments must target the underlying processes involved. For RA, that means altering immune function; for fibromyalgia, it means targeting the dysfunction of brain chemicals (neurotransmitters).

Managing RA

Many drugs are available for treating RA. They include:

• Disease-modifying antirheumatic drugs (DMARDs): Trexall/Rheumatrex (methotrexate), Imuran (azathioprine), and Azulfidine (sulfasalazine)
• TNF blockers/Biologics/Biosimilars: Enbrel (etanercept), Remicade (infliximab) and Humira (adalimumab)
• JAK Inhibitors: Xeljanz (tofacitinib), Olumiant (baricitinib), Rinvoq (upadacitinib)
• Glucocorticoids: Prednisone and methylprednisolone
• Non-steroidal anti-inflammatories (NSAIDs): Motrin/Advil (ibuprofen), Aleve (naproxen)
• COX-2 inhibitors (rare): Celebrex (celecoxib)

The treatment regimen may also include steroid injections, physical therapy, massage therapy, and lifestyle modifications.

Sometimes, surgery may be performed to help people with severe joint damage.

Managing Fibromyalgia

Common drugs for treating FMS include:

• Serotonin-norepinephrine reuptake inhibitors (SNRIs): Cymbalta (duloxetine), Savella (milnacipran)
• Anti-seizure drugs: Lyrica (pregabalin), Neurontin (gabapentin)
• Tricyclic antidepressants: amitriptyline
• Analgesic painkillers: Vicodin (hydrocodone acetaminophen), Oxycontin (oxydocone)
• Other medications: Xyrem (sodium oxybate), low-dose Naltrexone

Other common treatments include:

• Supplements (Vitamin D, B12, Omega-3, 5-HTP, rhodiola rosea)
• Myofascial release
• Acupuncture
• A specially tailored, moderate exercise program
• CBD oil

Managing Both

If you're taking medications for both RA and FMS, be sure to talk to your doctor and pharmacist about possible drug interactions.

Some FMS experts believe that the corticosteroids sometimes used to treat RA can make FMS symptoms worse, but thus far that's not proven; at the very least, they're ineffective against fibromyalgia symptoms.

According to Dr. Zashin, "The best course of treatment for patients who have both fibromyalgia and rheumatoid arthritis is to first treat the rheumatoid arthritis, since rheumatoid arthritis is commonly associated with joint deformity and disability. Slowing progression of rheumatoid arthritis and preventing permanent joint damage is the priority."

In addition, reducing your RA pain is likely to help ease FMS symptoms, as well.

Lifestyle Modifications

Making healthy changes to your lifestyle may help you manage both RA and FMS. The basics of a healthy lifestyle include:

• Not smoking
• Getting plenty of sleep
• Learning how to manage stress
• A moderate, low-impact exercise regimen
• A healthy diet, and possibly an anti-inflammatory diet

A Word From Verywell

Both RA and FMS can be limiting. By finding and following a treatment/management regimen, you may be able to preserve your functionality and independence.

Because both conditions can lead to depression and isolation, it's important for you to have a support system. Keep lines of communication open with your doctor and the people you're close to, and get early help if you think you're becoming depressed. Support groups—both online and in your community—may be a big help to you, too.