Psoriatic Arthritis: Recognizing the Key Features
MARCH 09, 2017
MD Magazine Staff
Allan Gibofsky, MD: Psoriatic arthritis is an unusual condition that occurs in patients with psoriasis. While most of the time the skin disease antedates the joint symptoms, in a minority of patients, the skin disease occurs simultaneously. And in some patients, the skin disease may occur after the joint disease. While many patients with psoriasis have joint pain and are often referred to the rheumatologist, thinking that it’s psoriatic arthritis, in fact, it may not be. Psoriatic arthritis is a true inflammatory condition that is a result of the psoriatic process going on elsewhere in the body. There are a variety of inflammatory mediators, called cytokines, that are abnormal in both the skin and the joints. And it is this abnormality that leads to the clinical presentations that we see.
Psoriatic arthritis has 5 main clinical presentations. The most common is asymmetric, meaning that the disease occurs on both sides of the body or in the top and the bottom of the body, but not necessarily in the same joints, simultaneously. The second is a symmetric form of arthritis, where the disease does occur in both joints on the same or different sides of the body almost mirroring each other. And this is a less common presentation, often confused with rheumatoid arthritis.
Then there is a peripheral form of arthritis affecting just the joints in the hands or the feet. There is an axial form of psoriatic arthritis affecting, primarily, the back and the sacroiliac joints. And this is often confused with ankylosing spondylitis or axial spondyloarthropathy. Finally, there is the more dreaded and complicated form of the disease, called arthritis mutilans, where, as its name applies, the joints are virtually mutilated.
One may see thickening of the entheses, which is the insertion of tendon into bone. The most common area for this so-called “enthesopathy,” or inflammation or illness of the enthuses, is the Achilles tendon. But, of course, other tendons can be involved as well.
Another clinical feature of psoriatic arthritis that may present at any time is inflammation of the eye—uveitis. Uveitis that is not caused by an infection is almost always a clinical feature of an underlying rheumatic disease. The challenge is figuring out which one it is, because we now have effective therapeutics to deal with that condition. If an individual presents to their general physician with pain, the medical history should include, among other things, the location of the pain, the duration of the pain, whether there are any other symptoms that are occurring with the pain, whether there is any skin involvement, whether there is any bowel dysfunction, and whether or not there are any other members of the family who have had a similar illness at any time in the past. The diagnosis of psoriatic arthritis is strengthened with the knowledge that a family member had something similar.
In addition, one often looks for a biomarker. There is no good biomarker for psoriatic arthritis. Indeed, some may say there is no biomarker for psoriatic arthritis. The diagnosis of high index of suspicion is generally made by the absence of a biomarker, and that is the serum rheumatoid factor—which is generally part of any arthritis panel that a general physician will do. So, if the general physician does an arthritis panel and the rheumatoid factor comes back negative, and the patient has joint pain—predominantly, but not necessarily exclusively, asymmetric—the physician should suspect that this very well could be psoriatic arthritis (especially if the patient also has psoriasis). But even if the patient doesn’t also have psoriasis, a negative rheumatoid factor coupled with joint pain that appears inflammatory in nature is a clinical condition that should be referred to the appropriate physician for differentiation and diagnosis. And the appropriate physician to differentiate joint manifestations is, of course, the rheumatologist.
Transcript edited for clarity.