Psoriatic arthritis (PsA) can sometimes seem like the master of disguises, mimicking other chronic conditions—and that can make it all the more difficult to get a diagnosis. In fact, 70% of people with PsA had up to a two-year delay in getting diagnosed, with delays longer than six months leading to increased joint damage and less successful treatment, according to the National Psoriasis Foundation (NPF). And when you’re in pain, any amount of time is too long to wait.
Keep reading to learn why PsA is so often confused for other conditions, how you can tell the difference, and what you need to do to get quick and accurate diagnosis.
What Is PsA, and Why Is It So Hard to Get Diagnosed?
PsA is a type of arthritis in which the immune system attacks the joints by mistake, leading to painful symptoms like stiffness and swelling. It’s associated with psoriasis, which is an inflammatory skin condition that can cause scaly patches on the body, says Minna Kohler, M.D., director of the rheumatology musculoskeletal ultrasound program at Massachusetts General Hospital in Boston.
Most people are diagnosed with psoriasis years before they get diagnosed with PsA, Dr. Kohler says. The majority of people with PsA have psoriasis; and while it’s not super common, it’s also possible to have PsA without having psoriasis, says the NPF. That said, having psoriasis doesn’t guarantee you will get PsA: Only about 30% of people with psoriasis also develop PsA.
Often, PsA is misdiagnosed as something else, delaying your ability to get the treatment you need. This is particularly likely if you don’t have obvious psoriasis symptoms, or you’re in the 15% of people with PsA and psoriasis whose arthritis symptoms show up before any skin symptoms, according to the arthritis nonprofit Creaky Joints. Without those skin manifestations, it can be tricky to pinpoint PsA as the cause of your symptoms.
There are a few key reasons why PsA gets misdiagnosed, whether you have psoriasis or not. For one, there’s no blood test that specifically tests for PsA, says Dr. Kohler. The other main factor is that PsA symptoms can look a heck of a lot like other diseases.
“Psoriatic arthritis can be misdiagnosed with other forms of arthritis,” says Celine Ward, M.D., assistant professor in the division of rheumatology and immunology at the Medical University of South Carolina in Charleston. Let’s take a look at these other conditions and the key differences between them and PsA.
PsA vs. Rheumatoid Arthritis
Rheumatoid arthritis (RA), like PsA, is an inflammatory type of arthritis related to problems with the immune system, according to the NPF. Both may appear similar on the surface, but there are key differences when you look deeper. Here are some of the main ones:
Symmetry. RA is usually symmetrical, meaning if your right wrist is affected, your left wrist probably is too. PsA, on the other hand, is often asymmetrical.
Different joints. “The distribution of joint involvement differs in PsA versus RA,” says Dr. Kohler. One example is in the spine: RA is more likely to affect the cervical spine (the neck), whereas PsA is more likely to affect the axial spine (low back). Also, get to know the word enthesitis, a.k.a. inflammation in the areas where tendons or ligaments attach to your bone: This characteristic is way more common in PsA.
Differing additional symptoms. Beyond the joint pain, which can look super similar in these two diseases, there are other symptoms that RA and PsA don’t typically share. For example, RA is more likely to come with bone erosion, while PsA can come with nail dystrophy (splitting, peeling, or yellowing) and, you guessed it, psoriasis. The big takeaway here is if you have psoriasis, your arthritis symptoms are more likely to be PsA than RA.
- Blood test results. While there’s no blood test for PsA, you can use blood tests to help rule out RA. If you have PsA and you’re tested for rheumatoid factor and cyclic citrullinated peptide antibodies (two tests common in RA diagnosis), you’ll likely have negative results. On the other hand, 80% of people with RA test positive for these.
Treatments for PsA and RA are similar—including nonsteroidal anti-inflammatory drugs (NSAIDs), steroids, and biologics—but because of all the differences in these two conditions on a microscopic level, they may respond differently to meds—so it’s important to get the right diagnosis.
PsA vs. Gout
Gout is another type of inflammatory arthritis, but unlike PsA, it’s related to having high levels of uric acid in the body, says Dr. Kohler. Crystals of that uric acid can then form in different parts of the body, causing symptoms.
PsA and gout do have symptoms in common, which explains the confusion. But here are some distinct ways gout differs from PsA, according to Creaky Joints:
Different pain patterns. PsA is more likely to be progressive, meaning it gets worse over time, whereas gout is episodic, meaning pain and stiffness come in episodes that last up to two weeks.
Different parts of the body. Both conditions can affect the toes and fingers, but if you’re having joint pain in other parts of the body like the neck, lower back, or hips, it’s probably PsA. If your pain is primarily in your big toe, that screams gout.
Time of day. PsA pain is often worst in the morning when you wake up, whereas gout pain often begins in the middle of the night.
But remember this: “It is notable that both PsA and psoriasis are associated with an increased risk for gout, so it is possible that some patients have both conditions,” says Dr. Kohler.
PsA vs. Osteoarthritis
Usually, when people say “arthritis,” they’re talking about osteoarthritis (OA)—the most common type of arthritis that often occurs with age and wear and tear on the body.
“Psoriatic arthritis patients often have similar bony changes that can be seen in osteoarthritis, and joint symptoms can sometimes look similar,” says Dr. Kohler.
That said, there are some big differences between PsA and OA:
Age. Unlike PsA, osteoarthritis most commonly affects adults over 60, according to the NPF. PsA most commonly develops between ages 30 and 50.
Root of the joint pain. Whereas PsA pain comes from joint inflammation thanks to the faulty immune response, pain from OA is the result of degeneration of the joints, often from injury or overuse, according to the CDC. “Psoriatic arthritis also can have other inflammatory features not seen with osteoarthritis including enthesitis, inflammation of tendon insertions, and dactylitis (soft tissue swelling of entire digits, also known as sausage digits),” Dr. Kohler adds.
Bone changes. “PsA is more associated with bony proliferation and bony growth than typical degenerative osteoarthritis,” Dr. Kohler says. These are growths or irregularities that develop on the bone; they may only be visible on X-rays.
- Differences in joint stiffness. While PsA and OA can both result in morning stiffness, it typically doesn’t last as long with OA: OA morning stiffness usually dissipates within 30 minutes, according to Creaky Joints, with PsA stiffness lasting up to an hour.
How Do You Get a Timely and Accurate Diagnosis?
If you suspect PsA, you’re probably eager to find out for sure—because the sooner you’re diagnosed, the sooner you can get treatment for your pain. Plus, leaving PsA untreated can lead to permanent joint damage. So how do you get the correct diagnosis…fast? It often comes down to whether your doctor is knowledgeable of PsA.
“It’s important that dermatologists and primary care physicians caring for patients with psoriasis ask about joint pain, morning stiffness, nail changes, and evidence of dactylitis (‘sausage’ digits) and refer them early to rheumatologists to avoid a delay in diagnosis,” Dr. Ward says.
Make sure your rheumatologist is well-versed in PsA, too: “Seeing a rheumatologist who is familiar with psoriatic arthritis and seronegative spondyloarthropathies (arthritis with negative rheumatoid blood tests) can help with making a timely and accurate diagnosis,” says Dr. Kohler.
A doctor who is thorough is also more likely to help you get a fast, accurate diagnosis. Once you get in the room with a good rheumatologist, they’ll likely collect your medical and family history and do a physical exam, blood tests, and imaging tests to diagnose you. For example, your doctor should ask you questions regarding any skin issues that could indicate psoriasis if you’re not already diagnosed, Creaky Joints says. Taking time to check you for things like nail symptoms, including yellowing or brittleness, that can be easy to miss is also a good sign.
“Since there are no specific biomarkers for psoriatic arthritis, diagnosis can sometimes be difficult, but both ultrasound and magnetic resonance imaging (MRI) can be used to identify enthesitis and dactylitis, which are two hallmarks of psoriatic arthritis, as well as other features such as enhanced blood flow or joint damage (erosions),” Dr. Ward says. Your doctor may also need to test the fluid from your joint to confirm PsA, she says. They’ll look for clues in the fluid, such as white blood cells that may point to inflammation.
Last but not least, don’t be afraid to advocate for yourself in the doctor’s office. If you’re experiencing symptoms, don’t delay—ask your doctor for a rheumatologist referral if they don’t offer one up, says Creaky Joints. Once you’re diagnosed, you’ll get on the road to managing your PsA and feeling better. And some good news: Treatments for PsA are getting better and better.
“In the past decade, there has been expansive growth in the number of biologic medications that are available for treatment of PsA and psoriasis,” Dr. Kohler says. “These medications have been successful in treating both skin and joints so that patients can preserve their joint function, reduce inflammation, treat pain, and improve quality of life.”