The Basics of Psoriatic Arthritis: An Interview with Dr. Gladman


In an effort to understand more about psoriatic arthritis, and how it is similar and different from rheumatoid arthritis, we decided to interview Dafna D. Gladman, M.D. F.R.C.P.C., Professor of Medicine, University of Toronto, on the basics of psoriatic arthritis. Let us know if you have more questions in the comments

What is psoriatic arthritis?

Psoriatic arthritis is an inflammatory arthritis associated with psoriasis, and usually sero-negative for rheumatoid factor.

Test criteria for psoriatic arthritis, which was developed by an international group, assigns points based on presentation.  Psoriatic arthritis is also an inflammatory musculoskeletal disease. If you have three of six points, psoriatic arthritis is considered. These points are based on things such as whether you have psoriasis, negative rheumatoid factor, x-rays, etc.  For example, if you  currently have psoriasis you get 2 points. Other things count for 1 point.

What causes it?

If I knew that, I would get a Nobel prize. We don’t know what causes it, but we have ideas about factors. Genetic factors are important, a number of genes have been incriminated in susceptibility to the disease. Psoriasis is a predisposing factor. We know that there may be some environmental factors that are relevant. For example, we have just recently shown that heavy lifting and infection requiring antibiotics are more common in patients with psoriatic arthritis than those with psoriasis alone. Interestingly, Smoking is lower among patients with psoriatic arthritis compared to those with psoriasis.

A third component is the immune response and whether that’s related to environmental factors.  There are some immune abnormalities; it’s an immune- mediated disease.

What comes first, the psoriasis or arthritis?

People with psoriasis primarily; 85 percent have psoriasis first.

Who gets psoriatic arthritis (gender, age etc.)?

In terms of gender, it’s an equal opportunist. The majority of patients are diagnosed in their 30s, but it can occur at any age.  The mean age is 36, but it can affect any gender, any age.

What are the symptoms?

It has the symptoms of inflammatory arthritis, pain, swelling, stiffness, and occasionally heat over the joint.  In addition, there is prolonged morning stiffness, night pain, which causes them to have to move around to get better.

These affect both peripheral joints and the spine. 50 percent of patients have involvement of the spine. Another major component is that dactylitis can occur, where the whole toe or finger can be red or tender.  This occurs in 50 percent of patients. A second component is inflammation primarily of the Achilles tendon, plantar fasciitis and heel bone.  However, it can affect other sites of the body as it is a musculoskeletal disease.

There are other forms of extra-articular features, such as skin and nails involvement, inflammation of the eye, inflammatory bowel disease, etc. There is an increased frequency of psoriasis with Crohn’s disease, which is partly genetic. Those are the main things.

How is PA diagnosed?

It’s not always all that easy, if one does not look for the psoriasis, they might miss that it’s psoriatic arthritis as opposed to rheumatoid arthritis. Psoriatic arthritis is more likely to present with asymmetric joint involvement, and a small number of joints.  The doctor would need to ask about psoriasis and other factors like ankylosis or dactylitis. That would facilitate the diagnosis, because there are no specific tests, as it is rheumatoid factor negative. One can also diagnose psoriatic arthritis on x-rays, because there are certain typical changes, but that means the doctor would have to order the x-rays.

How is PA different from rheumatoid arthritis?

Psoriatic arthritis has more asymmetric joint involvement upon early diagnosis, and there is involvement of end joints of fingers and toes. Psoriatic arthritis also affects the spine, while RA typically does not.

Other differences are that psoriatic arthritis does not have nodules, while RA does, and a rheumatoid factor is typical in rheumatoid arthritis, but not for psoriatic arthritis. In addition,  HLA-B27, an antigen associated with certain inflammatory diseases, is more typical for psoriatic arthritis rather than rheumatoid arthritis.

The joint inflammation for both diseases is similar, but patients don’t often have a reddish discoloration of the joints in rheumatoid arthritis.

How is PA treated?

It depends on what the patient has, if it’s primarily joint disease and inflammation, then disease modifying drugs, such as methotrexate would be used. Biologic agents would be used if they have more severe skin disease, and would be given NSAIDs for the arthritis. If there is severe skin disease and severe arthritis, we would use medications that work for both.  Methotrexate and anti-TNF agents would be the drugs of choice.

What are some tips for managing PA?

First tip: Go to the doctor as soon as you have symptoms, early diagnosis and early treatment is key.

Second tip: Make sure to get the correct diagnosis

Third tip: Make sure your doctor is treating the skin and the joints

It’s also important to recognize that psoriasis is not just a skin disease. Patients with psoriasis and psoriatic arthritis are at risk for heart disease, metabolic syndrome, they are  likely to be obese, and may have other comorbidities. The idea is that when we manage these patients, we need to make sure they don’t have high blood pressure and high lipids, so we reduce the risk factors for heart disease. And it’s also been found that predilection for heart disease and metabolic syndrome is related to severity of psoriasis. Chronic inflammation is a setting for developing all these other complications, and we need to turn it off.

I think it’s also important to know that there is an international group called GRAPPA (Group for Research and Assessment of Psoriasis and Psoriatic Arthritis), whose mission is to make life better for psoriasis and psoriatic arthritis patients. It’s a group of dermatologists and rheumatologists working together to solve problems.