Distinguishing Clinical Features in Psoriatic Arthritis

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In this segment, Philip J. Mease, MD, outlines the presentation and diagnosis of psoriatic arthritis, including how the clinical features differ from those of rheumatoid arthritis.

Philip J. Mease, MD: Psoriatic arthritis is an inflammatory arthritis that occurs in people with psoriasis. We know that psoriasis occurs in about 3% of the population of the United States, and psoriatic arthritis occurs in up to 30% of people with psoriasis. So, it’s not an uncommon inflammatory arthritis. It’s characterized primarily by peripheral inflammation of joints, but also there can be inflammation where tendons insert into the bone. There can be swelling of a whole digit, and there can be spine disease with inflammation of the spine, as well as the skin, and fingernail, or toenail manifestations of psoriasis.

It can be a devastating disease in some people with crippling changes, having a huge impact on function and quality of life. And in others it can be quite a mild problem, easily controlled, and not represent a great problem for that person. So, we really have to take into account the individual patient when we’re working on issues around education and management of the disease. And ultimately, these days we have the great capability of controlling many of the aspects of the disease and even putting it into remission.

The main way in which psoriatic arthritis presents is typically either as an inflammation of joints—say the fingers or wrist, or shoulders, or feet—or inflammation where a tendon or a ligament inserts into the bone, such as the Achilles’ tendon or plantar fascia in the heel.

A person often presents with just a couple or three joints involved, or perhaps one or two areas of what we call enthesitis, where the ligaments attach. But then gradually over time more and more joints, or more and more enthesis sites, may be involved. And also, sometimes we’ll see people presenting or eventually developing inflammatory spine pain with spondylitis. Usually this is in the context of somebody who already has psoriasis, but sometimes the arthritis will occur at the same time as the psoriasis, or even sometimes preceding the psoriasis.

This affects men and women equally and tends to begin in a person’s 30s or 40s, but sometimes it can first appear later in life as well. The condition is painful and will limit function in many people, but in some people, they may not be that limited in function.

Let’s start with some of the clinical features that are different between psoriatic arthritis and rheumatoid arthritis. For one, oftentimes when joints are involved, the involvement is asymmetric—meaning that a joint on one side of the body may not be involved on the other. Whereas in rheumatoid arthritis, it’s the other way around. Oftentimes there’s symmetric involvement with the same point being involved on both sides of the body.