This Is the Difference Between Rheumatoid and Psoriatic Arthritis
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Psoriatic arthritis is a type of arthritis that develops in some people who have psoriasis, which is a chronic autoimmune disease of the skin.
Psoriatic arthritis can be mild or severe. It can also be somewhere in between. But it’s important to understand that it’s a progressive disease. Although there are some very effective treatments to help you manage your condition and slow the progression, they can cause irreparable harm to your joints if left untreated.
To make things tricky, though, psoriatic arthritis can resemble another form of arthritis: rheumatoid arthritis. They can be hard to differentiate.
Related: These 20 Foods Will Reduce Inflammation and Relieve Arthritis Pain
Are you ready for this? It’s also possible to have psoriatic arthritis and other forms of arthritis, including rheumatoid arthritis. Yes, you can even have both psoriatic arthritis and rheumatoid arthritis at the same time. Since both are progressive diseases, it’s important to get the right diagnosis and know what you have so you can start treatment.
“The earlier the treatment, the earlier that we can stop the joint damage,” says rheumatologist Robert Hylland, MD, assistant clinical professor at Michigan State University College of Osteopathic Medicine.
Psoriatic Arthritis Explained
Not everyone with psoriasis develops psoriatic arthritis. According to the National Psoriasis Foundation, about eight million people in the United States have psoriasis. Research suggests that between 10 and 30 percent of people with psoriasis go on to develop psoriatic arthritis.
“Usually, but not always, psoriasis comes first,” says Erin M. Bauer, MD, a rheumatologist who practices in the Seattle area.
That means you’ll probably notice some plaques or scaly patches of psoriasis somewhere on your skin, first. However, there are occasions when a person will develop arthritis without noticeable signs of psoriasis first. It’s rare, but it’s possible.
Usually, psoriatic arthritis begins with some joint swelling like a finger or a toe, says Bauer. Dactylitis, which describes a digit that’s completely swollen like a sausage, is a common sign of psoriatic arthritis.
While it may start in the joints close to your fingernails or toenails, psoriatic arthritis can go on to affect other joints, too, including the knees and the elbows. A few people even develop inflammation and swelling in their spines, a condition known as psoriatic spondylitis.
How Psoriatic Arthritis Differs from Rheumatoid Arthritis
Rheumatoid arthritis is also a chronic autoimmune disease. You’re more likely to develop rheumatoid arthritis if you have a family history of RA. People over the age of 40 and women are also more at risk.
Experts haven’t pinpointed the exact cause of rheumatoid arthritis yet, but we do know that your body’s antibodies attack the joints if you have this condition. Typically, it affects the smaller joints first--the small joints in the hands, feet and wrists. It causes swelling, pain and stiffness in these joints.
So what makes it different from psoriatic arthritis? It can be tough to determine without bloodwork, as there can be some overlap with the joints that both kinds can affect, notes Bauer. For example, both can affect the hips and knees, Bauer says.
Related: The #1 Early Sign of Arthritis Most People Miss
If your doctor suspects you have rheumatoid arthritis, you may need to undergo some blood tests to look for high levels of inflammation and for specific antibodies that are commonly found in the bloodstream of people with RA. Among others, the doctors will be looking for evidence of an antibody called the Rheumatoid Factor (RF) antigen and perhaps also cyclic citrullinated peptide antibodies (CCP).
However, two things might help you distinguish the two types of arthritis from each other. One is fairly obvious: the presence of psoriasis lesions. That’s a cue that you’re probably dealing with psoriatic arthritis.
But the other factor is the location of the affected joints. While there is possible overlap, they can and do affect different joints. For example, psoriatic arthritis tends to affect the joints closer to your fingernails, known as distal interphalangeal joints. RA tends to affect the other joints in the hands, which are called the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints. It also tends to affect the wrists, and the metatarsophalangeal (MTP) joints, or the small joints in your feet.
RA also tends to affect the same joint on both sides of the body, while it’s more common for psoriatic arthritis to only affect joints on one side of the body.
Related: What Does Arthritis Feel Like?
“Rheumatoid arthritis tends to be more symmetric,” says Bauer. “So we’d expect to see it on both sides, whereas psoriatic arthritis is not symmetric. You could have just one knee and one elbow affected.”
Early Diagnosis and Appropriate Treatment
Now the good news: treatment has come a long way in recent years.
“There are several good treatment paradigms for psoriatic arthritis, and the likelihood of severe deformity like there was in the past is close to zero with the new therapies we have,” Hylland says.
There are also effective treatments for managing rheumatoid arthritis. And while it’s possible to have both psoriatic arthritis and rheumatoid arthritis at the same time, that won’t necessarily complicate your treatment plan.
“The initial treatments are the same for both,” says Bauer, noting that tumor necrosis factor (TNF) inhibitors work well for both types of arthritis, especially for people who can’t take methotrexate, which is another first-line treatment. (TNF inhibitors block the action of an immune system protein called TNF, which causes inflammation.)
Another med that can be used to treat either RA or psoriatic arthritis is a Janus kinase inhibitor, or JAK inhibitor, like tofacitinib. This type of drug interrupts your immune system’s urge to overproduce many inflammation-causing proteins called cytokines. They may work better for you than other kinds of drugs and they have the bonus of being available in pill form, rather than an injection or infusion.
With either condition, you mustn’t ignore the symptoms until they become very severe. Early diagnosis is critically important for slowing the progression of these diseases.
“The earlier we catch it, the less we have to do to quiet it--the less medication we have to use it quiet it,” says Hylland.
Next up: The One Food You Should Never, Ever Eat If You Have Chronic Inflammation
Sources:
Robert Hylland, MD, assistant clinical professor at Michigan State University College of Osteopathic Medicine
Erin M. Bauer, MD, a rheumatologist
