Diseases That Mimic Rheumatoid Arthritis

Diagnosing rheumatoid arthritis (RA) accurately is challenging—and not just because there's no one test that can confirm it. There is notable overlap between its symptoms—joint pain, stiffness, fatigue, and so on—and those of some viral and bacterial infections, other rheumatic or autoimmune diseases, and even other types of arthritis. As a result, RA is often confused for Lyme disease, lupus, fibromyalgia, or a number of other conditions that mimic RA.

Given this, ruling diseases and conditions like the following out is part of the process of diagnosing RA. This involves considering a combination of a physical examination, your medical history, laboratory test results, and imaging studies.

Even if you have been diagnosed with RA, there is always a chance that your diagnosis is incorrect. Doctors may consider another condition if you've been treated with disease-modifying anti-rheumatic drugs (DMARDs) but are not improving.

Research published in the Annals of the Rheumatic Diseases found that more than 40% of people who were given an RA diagnosis actually had a different condition.

It's also possible that you could have RA and another condition.

Man describing pain to a doctor
 Hero Images / Getty Images


The most common type of arthritis, osteoarthritis (OA) is a degenerative joint disease sometimes mistaken for RA. Some key differences in the presentation of OA from RA include:

  • The absence of systemic inflammation symptoms such as fever
  • Onset in older adulthood
  • An asymmetrical pattern of joint involvement

Blood work and imaging tests can help your doctor hone in on an accurate diagnosis. Patients with OA do not test positive for rheumatoid factor (RF), and RA and OA have distinctly different radiographic appearances.

Psoriatic Arthritis

Psoriatic arthritis (PA) and other spondyloarthropathies can present similarly to RA, but can often be distinguished through blood work.

High levels of rheumatoid factor (RF) or anti-citrullinated peptide (anti-CPP) antibodies are typically present in RA. These results are considered seropositive.

PA, reactive arthritis, ankylosing spondylitis, and inflammatory bowel disease–associated arthropathy do not have these indicators (seronegative).

In addition, RA typically starts in the fingers and toes, whereas PA and other spondyloarthropathies can affect the spine and the sacroiliac joints.

Other key characteristics that help differentiate PA include:

  • Asymmetrical joint involvement
  • Absence of small-joint disease
  • A sausage-like appearance of fingers or toes
  • Psoriatic rash, which may or may not be present

Viral Arthritis

Viral infections such as rubella, parvovirus B19, HIV, and hepatitis B and C can cause pain and swelling in multiple joints (polyarthritis) and present in a way that's clinically similar to rheumatoid arthritis.

Viral arthritis can be distinguished from RA by considering other symptoms (like a rash) and your history of exposure to specific viruses. For example, recent travel to Italy, India, Indian Ocean islands, or the Caribbean would indicate possible exposure to the mosquito-borne alphavirus chikungunya, which presents as joint pain, fever, and a rash.

Your doctor can take blood work to rule out different viral causes of joint pain. There is no specific treatment for viral arthritis other than pain management, except for HIV-triggered arthritis which can be relieved with combination antiretroviral therapy.

Most cases of viral arthritis resolve on their own after several weeks.

Lyme Disease

The tick-borne illness Lyme disease presents with joint pain and swelling and can be mistaken for RA. Caused by the bacteria Borrelia burgdorferi or Borrelia mayonii, the first sign of Lyme disease is a bull's-eye rash (present in 70% of cases) that appears three to 30 days after a bite from an infected tick.

Left untreated, Lyme disease results in arthritis with severe joint pain and swelling, particularly in the knees and other large joints.

Other signs of Lyme disease that differ from those of RA include:

Lyme disease is diagnosed based on blood work to test for antibodies. However, it takes several weeks for the immune system to develop enough antibodies to be detected, so a recent infection may not appear positive. The test should be repeated in about six weeks.

Early treatment of Lyme with antibiotics typically results in complete recovery, though symptoms can linger for up to six months. A delay in antibiotic treatment can make the disease more difficult to treat and may result in chronic symptoms and pain, so it's important that any symptoms be investigated.


The chronic-pain condition fibromyalgia can be misdiagnosed as RA. Both can involve symmetrical joint pain and stiffness, but with fibromyalgia, the pain is only at rest and not exacerbated by joint use. 

Imaging studies are useful for distinguishing fibromyalgia from RA, notably due to the absence of synovitis (inflammation of joint lining). In addition, blood tests for fibromyalgia are seronegative.

Fibromyalgia also differs from RA in the following ways:

Fibromyalgia can be difficult to diagnose and may take several visits and different doctors. There are no specific tests to confirm a diagnosis and, much like with RA, it is important to rule out other possible conditions.

Lupus and Scleroderma

The autoimmune diseases systemic lupus erythematosus and scleroderma often present with joint involvement that mimics rheumatoid arthritis. While lupus and scleroderma are two different diseases, they often overlap with one another.

One key difference between arthritis and lupus/scleroderma is the source of joint pain and deformity.

In arthritis, damage to synovial fluid and bone erosion causes pain. In lupus and scleroderma, joint pain and deformity are due to damaged connective tissue in ligaments and tendons. These differences are typically evident on imaging tests.

People with lupus and scleroderma may also test seropositive and blood work may not help differentiate between them and RA.

Other signs of lupus and scleroderma not common in arthritis include:

  • Raynaud’s phenomenon of painfully cold fingers and toes with a pale-white or blue hue caused by poor circulation
  • Esophageal dysfunction or other digestive problems
  • Sjögren’s syndrome, which affects fluid-producing glands such as tear glands and salivary glands


Crystal-deposition diseases like gout and pseudogout are often mistaken for RA. Caused by an abundance of uric acid, crystal deposits settle around affected joints resulting in inflammation and tissue damage.

Gout tends to appear as painful, swollen joints associated with asymmetric inflammation in one or more fingers or toes. A gout attack commonly affects the large toe and lasts three to 10 days.

Over time, gout attacks can become more frequent, last longer, and may not resolve. This can lead to chronic gouty arthropathy, which can cause erosions and joint destruction.

Calcium pyrophosphate deposition disease (CPPD) or pseudogout (false gout) is a type of arthritis that can present similarly to gout or RA but is distinguishable by acute attacks of synovitis akin to gout.

Tests your doctor may perform to differentiate between gout, CPPD, and RA include blood tests for uric acid, imaging tests, and synovial fluid analysis.

Reactive Arthritis

A painful form of inflammatory arthritis, reactive arthritis is caused by a bacterial infection of the genitals or bowels. It commonly affects the heels, toes, fingers, low back, knees, or ankles.

Previously known as Reiter's syndrome, reactive arthritis is in the family of seronegative spondyloarthropathies. It may be indicated if symptoms appeared within a month of a bout of diarrhea or a genital infection.

Your doctor will likely draw blood to test for common bacterial infection, such as Chlamydia trachomatis, Campylobacter, Salmonella, Shigella, or Yersinia.


Bursitis is an inflammation of the small, fluid-filled sac (bursa) that acts as a cushion between a bone and other moving parts. Caused by overuse or injury, it results in joint pain and inflammation that can be mistaken for RA.

Bursitis typically affects only one joint at a time—commonly the knee, elbow, or shoulder—and does not have systemic symptoms that can be common in RA (e.g., fever).

Diagnosis is based on physical examination and imaging tests such as X-rays or MRIs. Your doctor may take fluid from the swollen area to rule out an infection as well.


Sarcoidosis, an inflammatory disease that typically affects lungs, skin, or lymph nodes, can be misdiagnosed as RA. Characterized by tiny, grain-like lumps (granulomas), sarcoidosis can manifest with synovitis in several joints and may be seropositive.

Like RA, sarcoidosis onset typically occurs between ages 30 and 50.

Other characteristics of sarcoidosis that help to distinguish it from RA include: 

Sarcoidosis is formally diagnosed through biopsy.


Vasculitis, an inflammation of blood vessels caused by an autoimmune response, can affect joints and be misdiagnosed as RA.

Two types of vasculitis, polymyalgia rheumatica (PMR) and giant cell arteritis (GCA), can occur with symmetrical polyarthritis. In addition, people with vasculitis often test seropositive for rheumatoid factor.

The key difference is vasculitis commonly presents with headaches; a detailed medical history can help distinguish PMR or GCA from RA. For example, a headache, along with shoulder and hip pain may indicate vasculitis.

In some cases, a diagnosis of vasculitis may depend on the observation of the disease over time, particularly if complications develop.

Dual Diagnosis

You may be so used to your RA symptoms that you chalk up any compounding of them to the disease, rather than another possible cause.

If you are experiencing an unusual persistence of or increase in your RA symptoms, or new ones are appearing, be sure to check in with your doctor. Additional diagnoses can be considered and, at the very least, you can be evaluated to see if a modification of your RA treatment plan may be necessary.

While any of the above are possible, the most common RA comorbidities—which may/may not have similar symptoms—are:

  • Cardiovascular disorders
  • Gastrointestinal disease
  • Renal diseases
  • Pulmonary diseases
  • Infections
  • Osteoporosis
  • Tumors
  • Depression

A Word From Verywell

Joint pain is a common symptom in many conditions that can mimic rheumatoid arthritis and complicate getting an accurate diagnosis. If you are not satisfied with your diagnosis or treatment, talk to your doctor. It may be necessary to request additional testing or ask for a referral to a rheumatologist or other specialist.

As a patient living with joint pain, you are your best advocate. Ensuring an accurate diagnosis is essential for finding a treatment that works for you.

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