Swollen knuckles, aching joints, fatigue, stiffness that lasts for more than an hour, and a decline in range of motion; these symptoms may mean you have rheumatoid arthritis, or they could be signs of something else entirely. According to Natalie E. Azar, MD, clinical associate professor of medicine and rheumatology at the NYU Grossman School of Medicine in New York City, there are key differences to look for between RA and several of the health conditions that mimic symptoms of the autoimmune disease. If it’s not rheumatoid arthritis, what else might it be?
Lupus
Lupus, or systemic lupus erythematosus (SLE), is a chronic autoimmune disease that affects many parts of the body, including the joints, skin, blood vessels, and internal organs. Though lupus is not a form of arthritis, arthritis is one of its most common symptoms, according to the Lupus Foundation of America. "The arthritis of lupus can mimic very closely that of rheumatoid arthritis," notes Dr. Azar, "but in contrast to RA, SLE does not cause an erosive, deforming arthritis and joint symptoms tend to be milder overall.”
Lyme Disease
Fever, stiffness, body aches, and fatigue often accompany Lyme disease, the most common tick-borne infectious disease in the United States. In the early phases of this health condition, you may feel all-over joint and muscle pain without the noticeable signs of inflammation such as warmth, redness, and swelling. With advanced Lyme disease, 1 in 4 people develop what's called monoarticular inflammatory arthritis — typically one large, swollen joint, often the knee, according to the Centers for Disease Control and Prevention. It's possible to have RA in just one large or small joint on only one side of the body rather than have it affect the same joint on both sides, but this is "the exception rather than the rule," says Azar.
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Gout
High levels of uric acid in the blood put you at risk for gout, a very painful type of inflammatory arthritis. Your doctor may suspect this health condition if your symptoms — intense pain, swelling, warmth, and redness — begin in your big toe. While this is the typical joint involved, gout can attack virtually anywhere, including the foot and ankle, knees, wrists, elbows and fingers, notes the Mayo Clinic. If gout goes untreated, it can cause erosive, deforming arthritis, which can mimic RA. Soft tissue deposits of uric acid crystals called tophi may appear on the ears as well as surfaces such as the elbows, according to CreakyJoints. "Rheumatoid nodules can have a similar distribution in the extremities,” notes Azar.
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Ankylosing Spondylitis
Ankylosing spondylitis is a progressive form of arthritis caused by chronic inflammation of joints in the spine. This type of arthritis belongs to a group of disorders called seronegative spondyloarthropathies. Seronegative is the term used when a patient tests negative for the autoantibody known as rheumatoid factor, a measure used to help diagnose rheumatoid arthritis. With spondylitis, you'll typically experience inflammatory back pain, and pain that's worse in the morning and improves as the day goes on, explains Azar. It gets better with exercise and responds to NSAIDs, or nonsteroidal anti-inflammatory drugs.
Reactive Arthritis
Formerly known as Reiter's syndrome, reactive arthritis occurs from a bacterial infection in the body, according to the American College of Rheumatology. An inflammatory reaction typically starts within two to four weeks after the infection and arthritis symptoms may come and go over several weeks to months, per the Arthritis Foundation, though it can be more severe and longer lasting. Reactive arthritis typically affects a few large joints, usually on one side of the body, notes Azar. You'll also notice inflammation of tendons, ligaments, and muscle attached to the bone, and swelling in fingers or wrists. Other possible symptoms include urethritis or inflammation of the urinary tract, conjunctivitis or inflammation of the eyes, fever, rash, and mouth ulcers. The main symptoms of reactive arthritis tend to go away after a few months, though some people will have symptoms for up to a year and others may have long-term mild arthritis. Rheumatoid arthritis, by contrast, is chronic, though in rare cases, notes Johns Hopkins Medicine, reactive arthritis can become severe and chronic.
Additional reporting by Deborah Shapiro.
Samir Dalvi, MD
Medical Reviewer
Samir Dalvi, MD, is a board-certified rheumatologist. He has over 14 years of experience in caring for patients with rheumatologic diseases, including osteoarthritis, rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, lupus, and gout.