Diseases That Mimic Rheumatoid Arthritis

A number of diseases can be similar to rheumatoid arthritis (RA). There is notable overlap between symptoms of RA—joint pain, stiffness, fatigue—and those of RA-like rheumatic or autoimmune diseases, other types of arthritis, and some viral and bacterial infections.

Ruling out other conditions that mimic RA, such as Lyme disease, lupus, and fibromyalgia is part of diagnosing RA. This process relies on a combination of your physical examination, medical history, laboratory test results, and imaging studies.

Even after you've been diagnosed with RA, your doctors may consider other conditions if are still not improving, despite treatment with disease-modifying anti-rheumatic drugs (DMARDs).

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

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

Man describing pain to a doctor
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Osteoarthritis

The most common type of arthritis, osteoarthritis (OA) is a degenerative joint disease that can be similar to RA.

Some key differences between OA and RA include:

  • The absence of systemic inflammation symptoms with OA
  • Onset in older adulthood with OA
  • OA affects different joints than RA (for example, the end joints of the hands are commonly involved in OA but not usually involved in RA)
  • An asymmetrical pattern of joint involvement with OA
  • With RA, prolonged morning stiffness typically lasts for over 45 minutes, while morning stiffness in OA often lasts for less than 30 minutes.
  • OA pian typically gets worse with activity, while RA pain often improves

Blood work and imaging tests can help your doctor hone in on an accurate diagnosis. Rheumatoid factor (RF) is usually present in RA but not in OA, 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 of PA that help differentiate it from RA 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 often be distinguished from RA by a rash and a history of exposure to specific viruses. For example, recent travel to Italy, India, Indian Ocean islands, or the Caribbean could have led to 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 and bacterial causes of joint pain. Treatment for viral arthritis is normally focused on pain management. And HIV-triggered arthritis can be relieved with combination antiretroviral therapy.

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

Lyme Disease

Lyme disease is a tick-borne illness caused by the bacteria Borrelia burgdorferi or Borrelia mayonii. It presents with joint pain and swelling but can be mistaken for RA. 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 chronic arthritis with severe joint pain and swelling, particularly in the knees and other large joints.

Other signs of Lyme disease that aren't present in RA include:

Lyme disease is diagnosed based on antibodies, which can be identified with a blood sample. It takes several weeks for the immune system to develop enough antibodies to be detected, so a recent infection may not produce a positive test. If you could have this condition your test will likely be repeated in about six weeks.

Early treatment of Lyme disease 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.

Fibromyalgia

Fibromyalgia, a chronic pain condition, can be misdiagnosed as RA or another rheumatic condition. Both RA and fibromylagia can involve symmetrical joint pain and stiffness, but with fibromyalgia, the pain occurs at rest and not exacerbated by joint use. 

Imaging studies are useful for distinguishing the conditions because synovitis (inflammation of joint lining) is present with RA and absent with fibromyalgia. In addition, blood tests for fibromyalgia are seronegative.

Fibromyalgia also differs from RA because it causes:

Fibromyalgia can be difficult to diagnose. 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, deficient synovial fluid and bone erosion cause 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, so blood work may not help differentiate between them and RA.

Other signs of lupus and scleroderma that aren't common in arthritis include:

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

Gout

Crystal-deposition diseases like gout and pseudogout are often mistaken for RA. With these conditions, 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 for 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 from acute gout attacks.

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. Symptoms generally appear within a month of a bout of diarrhea or a genital infection.

A blood test can identify bacterial infections, such as Chlamydia trachomatis, Campylobacter, Salmonella, Shigella, or Yersinia.

Bursitis

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, the condition causes 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 the systemic symptoms of RA.

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

Sarcoidosis

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

Vasculitis, inflammation of blood vessels caused by an autoimmune process, can affect joints and might mimic 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.

A key difference is that 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 observation of the disease over time, particularly if complications develop.

Dual Diagnosis

You may be so used to living with RA that you chalk up any change in your symptoms to the disease, rather than another possible cause.

If you are experiencing an unusual persistence of or increase in your RA symptoms, or if 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 it's possible that you could also have any of the common RA-mimics, 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, a common symptom of many conditions that can mimic rheumatoid arthritis, may complicate the diagnosis. If you aren't improving with treatment, talk to your doctor. You might need additional testing or 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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