Psoriatic Arthritis

Psoriasis is a skin disorder of dry flaky skin on top of a red base that occurs on the elbows or the scalp, and sometimes on the hands and feet. That’s how most people know the problem. But there are many people with psoriasis who get arthritis and generalized aches and pains, and it’s all related to the skin problem.

There seems to be genetics involved. Psoriasis runs in families, and sometimes skips a generation, so that maybe your father had it too, but perhaps it was a grandparent instead. Having the skin problem by no means is a sign that you’re going to develop joint trouble, but what’s interesting is that relatives of people with skin disease can develop joint pains without psoriasis as a result of the genetics that are passed on in the family.

People who develop psoriasis generally develop joint disease (if they get it at all) within about 8 years of the skin problem showing up. Those who get the joint pains first may develop skin problems only about two years later.

It’s not just the skin that’s involved with psoriasis. The nails can show the illness, too. Psoriasis involving the nails can cause pitting on the surface of the nail. It can cause the nail to lift up from the nail bed, causing the edge of the nail to show white crescents curving toward the growing edge of the nail, a process called onycholysis. Occasionally, only the nails are involved, without evidence of skin disease.

Making the diagnosis of psoriasis arthritis/tendonitis means looking carefully for these nail changes, and also checking over the entire body for the characteristic flaky red skin that is the hallmark of psoriasis. It can even occur as a little dime-sized patch on the scalp, under the hair; many people think they have dandruff, when actually they have psoriasis. The skin changes can be found in the ear canal or behind the ears, and it’s pretty difficult to know you have the problem when you can’t see these areas to examine them.

Enough for the skin involvement. It can be widespread over the body and of course be a major problem medically and socially. But when the disease affects the joints, pain is often the worst of the illness. All the joints of the body can be involved with arthritis (swelling, redness, pain and heat to the touch)…both knees, both hands, both wrists, both ankles. Though the disease is less crippling in general than other inflammatory arthritis types, there can be serious joint damage in some patients, damage that can lead to disability.

But more likely than not, the arthritis can affect just a couple of joints…one knee, the opposite ankle, one wrist, and one finger on the opposite hand, for example. When the hands are involved, sometimes an entire finger becomes swollen and painful, every joint from the tip to the palm, and the digit resembles nothing less than a sausage. In fact, we sometimes refer to that kind of finger involvement as “sausage digits.” That’s also because not only are the joints inflamed, but the tendons all along the finger are inflamed, too (tendons are where muscles narrow down and attach to bones. They’re the shiny white stuff that you have to cut through in a tough piece of meat.)

A typical type of the arthritis is one which strikes only the tip joints of all the fingers, the DIP joints. There’s a type of osteoarthritis that can do this too, but in the setting of skin or nail changes of psoriasis, psoriasis arthritis may be the culprit.

This tendonitis, however, is one of the tip-offs that the diagnosis has to do with psoriasis. Any tendon in the body can be sore, the elbow tendons (“tennis elbow” is a common sign of psoriasis disease, if it happens in the setting of the skin problem or with multiple tendon inflammations), the tendons across the tops of the feet, the Achilles tendons especially and the plantar fascia on the bottoms of the feet. Plantar fasciitis is a very common problem in this disorder, by the way.

The leg joints are the most frequently involved, especially the hips, knees, ankles and feet, and often not symmetrically. A combination of arthritis in these joints and their tendons all inflamed at the same time is helpful in making the diagnosis.

The spine is a common place for pain to occur, especially the mid and low back. But the neck can be involved as well and the sacroiliac joints and the combination of affected joints has given a name to the disorder…psoriatic spondyloarthropathy. It means spine, tendon and joint pain due to psoriasis. As a matter of fact, because there are hundreds of tendons all over the body, patients frequently have pains all over, sometimes also in the joints, but sometimes just where all those tendons attach to bones.

Occasionally, an inflammation of the eye called uveitis or iritis can happen with psoriatic athritis. It's not common but it helps in figuring out the reason for the joint pain. Less common is another type of skin problems called erthyma nodosum, large painful red nodules under the skin along the shin aspect of the lower legs.

This presentation of just joint and muscle pain can lead to misdiagnosis; many patients are thought to have “fibromyalgia,” a type of non-descript muscle spasm, which is kind of a wastebasket term that doctors diagnose when they can’t think of anything else. Often, it’s really psoriasis tendonitis.

Confirming the diagnosis may be hard, because there are no particular blood tests that show up the problem. There are genetic tests for psoriasis, but there is no really close link between any one gene and the disease, so the results of genetic testing is iffy at best. Tests for inflammation may be normal, despite the fact that inflammation is at the base of the problem.

It’s mainly the doctor’s suspicion that the joint pains are related to the skin disease that is the best way to make the diagnosis. X-rays can help, though psoriasis involvement on the joints is not different than other inflammation-related arthritis such as rheumatoid arthritis.

But what is distinctive is the tendonitis component of the disease. Often the tendons all over the body are chronically inflamed, which over the years leads to bone spur formation of a typical type that can be seen on X-ray. Sometimes the spine is involved without pain, and patients with swollen knees and ankles that for all the world look like rheumatoid arthritis can be differentiated by the formation of typical psoriatic bone spurs seen on spinal X-rays. So don’t be surprised if your rheumatologist wants to take spine X-rays even if you don’t have pain there!

Getting patients back to normal health is the obvious goal of treatment, and modern anti-inflammatory drugs are the answer. NSAID’s are often great to treat mild disease. For severe problems, methotrexate used to be the best drug, and for some patients it remains so. But methotrexate just slows down the process of the disease, it doesn’t stop it.

The some of the biologic drugs do stop the progression of the inflammation and potential joint destruction. Luckily, these drug can also melt away the skin disease, so that people with arthritis and skin psoriasis often get a double effect. These drugs are so good at putting psoriasis into remission that dermatologists  send us patients for biologic drug infusions.

For more, see information on Psoriatic Arthritis from the Arthritis Foundation and the American College of Rheumatology.

© Jay Adlersberg 2015