9 Conditions That Mimic Rheumatoid Arthritis

First, let's talk about rheumatoid arthritis. RA is a inflammatory autoimmune disease that primarily affects the lining of your joints. It usually affects small joints first, and it's nearly always symmetrical (meaning if you have swollen joints in one hand, you'll have them in the other as well). RA is also a systemic condition, which means it impacts your heart, lungs, eyes, and other organs. There’s no simple test to tell if you have RA, but it’s also super important to get an accurate—and early—diagnosis, says Orrin Troum, M.D., a rheumatologist at Providence Saint John's Health Center in Santa Monica, CA. Prompt treatment can prevent long-term damage and disability.

Some clues your provider will look for when trying to determine if you have RA include: joint stiffness that's worse in the morning; signs of inflammation (your joints are red and/or warm to the touch); and low-grade fever. If there’s any question whether RA is in play, a rheumatologist should be consulted—and quickly, says Dr. Troum. If you’re told it will take three months to get an appointment, ask your provider to call the rheumatologist on your behalf, requesting that you be seen urgently. During your appointment, your rheumatologist will look for signs of the chronic disease while also working to rule out the following conditions that often mimic RA.

What it is: Osteoarthritis (OA) is the most common form of arthritis, and it’s not unusual for someone with RA to get misdiagnosed with it.

How it’s different from RA: The main difference is that OA is non-inflammatory. It's caused by wear and tear on joints, whereas RA is an autoimmune disease that causes the body to attack its own cells. While both can cause morning stiffness, the discomfort with RA generally lasts longer, at least 30 minutes and up to several hours, says Lynne Peterson, M.D., a rheumatologist at the Mayo Clinic.

What it is: Gout, a form of inflammatory arthritis, can cause swollen joints that are so painful that even a bed sheet brushing against them will trigger intense pain. The condition is caused by too much uric acid in the blood and tissues.

How it’s different from RA: "Gout usually affects only one or two joints, most often the big toe," says Dr. Peterson. Also, patients often have a family history and symptoms are shorter-lived, dissipating in one or two weeks. That’s not the case with RA, where symptoms linger (even if they seem intermittent at first), Dr. Troum says.

What it is: There are five different types of psoriatic arthritis (PsA), including one that looks almost exactly like RA. "PsA is one of the conditions that is most often confused with RA," Dr. Troum says. They both produce pain, swelling, and redness.

How it’s different from RA: Eighty-five percent of people with PsA have psoriasis first. Other distinguishing features: PsA often causes changes to nails, such as pitting; swollen fingers that resemble sausages; and inflammation at the sites where tendons attach to the bones, Dr. Peterson says. And in PsA, pain is usually asymmetrical. In patients who don’t have those distinguishing symptoms, blood tests may help.

What it is: Parvovirus, also known as fifth disease, often presents with a unique “slapped-cheek” rash in kids. In adults, symptoms are more generic, leading to frequent misdiagnosis. The most common symptoms in adults are joint soreness and swelling, usually in hands, wrists, knees, and ankles (thus the confusion with RA). Adults with the infection are more likely than kids to run a fever, and they're less likely to exhibit the tell-tale rash.

How it’s different from RA: Symptoms usually last for a period of days or weeks. And, you’ll know you have parvovirus, not RA, from a blood test.

What it is: Chikungunya, a mosquito-borne virus that most often occurs in the Caribbean, Africa, India, and South and Central America, has recently become more common in the United States. Patients usually experience severe joint pain that can last as long as 12 to 15 months. For some, that pain continues for years; those are the cases most likely to be confused with RA.

How it’s different from RA: Infection usually causes a sudden high fever, rash, headaches, and muscle pain, along with joint pain and swelling, according to the World Health Organization. Always let your doctor know if you've traveled to any of the affected regions.

What it is: Lyme disease, an infection transmitted to humans by black-legged ticks, sometimes causes joint pain that can be confused with RA, especially when Lyme is untreated. If you suspect you’ve been bitten by a black-legged tick, it’s important to see a healthcare provider right away. (And if you find the tiny tick, remove it with a tweezers.)

How it’s different from RA: Joint paint from Lyme disease usually affects one or both knees, and rarely affects small joints, like those in the hands, Dr. Peterson points out.

What it is: Reactive arthritis can be triggered by an infection elsewhere in the body, such as the sexually transmitted disease chlamydia or a bacterial gastrointestinal infection. It can cause RA-like joint pain and swelling.

How it’s different from RA: The joints most commonly affected are the knees and those in the feet, but usually just on one side. More clues that it’s reactive arthritis and not RA: You're urinating more often and experiencing discomfort while doing so; you have swelling in your toes or fingers; and/or a rash on the soles of your feet or your palms.

What it is: This chronic central nervous system disorder causes widespread pain in the muscles and soft tissue. Fatigue and sleep disturbances are also common.

How it’s different from RA: "Fibromyalgia can be distinguished from RA by the source of the pain—muscles, not joints," Dr. Peterson says. Also, people with fibromyalgia may experience pain in a few locations that most RA patients do not, including the back of the head, the collarbone area, and buttocks. And some fibromyalgia patients experience memory problems, sensitivity to temperature, noise and light, and irritable bowel syndrome. Fibromyalgia can commonly co-occur with rheumatoid arthritis.

What it is: Lupus is also a chronic autoimmune disease that causes pain and swelling in joints, muscle aches, and fatigue. Adding to the challenge: Sometimes people can develop RA and lupus, which can make diagnosis extra difficult.

How it’s different from RA: Some distinguishing symptoms of lupus can help make the diagnosis: Some patients with lupus get a butterfly-shaped rash on the face, arms, legs and other sun-exposed areas; ulcers in the mouth or nose; and lab analysis may show excess protein in the urine that not common with RA.