More than 4.5 million adults suffer from psoriasis, a chronic condition that causes red, flaky patches of thickened skin. This uncontrollable overgrowth of skin cells can appear on the scalp, hands, feet and genitalia. But the lesions most commonly appear on the elbows, knees and lower back, which might give a hint as to why almost one third of psoriasis sufferers also have a compounding disease, psoriatic arthritis, which affects the joints and can be crippling.
Psoriatic arthritis, however, can be effectively treated in most patients if it is recognized early enough. Alan Menter, MD, chief of dermatology at Baylor Medical Center in Dallas, Texas outlines this potentially disabling disease and the treatments available for it.
Psoriatic arthritis is an inflammatory joint disease that is almost always associated with a skin disease called psoriasis. There are five different subtypes of the joint disease: anything from just a few swollen fingers and toes to more severe involvement of large joints to very disabling involvement where the hands and feet and the spine get pretty inflamed and chronically destroyed, actually. So, it''s a whole range from very minor disease to very severe disease, which can be disabling in about 20 percent of patients.
What causes psoriatic arthritis?
As with a lot of other diseases, there''s a genetic component, but there''s an environmental component as well, possibly illnesses, infections, stress. There are eight different genes associated with the skin disease, and some of those are also associated with the joint disease.
Psoriasis an immune-mediated disease, whereby T cells, are increased in number. As these cells circulate into the skin and the joints, they produce a chemical by the name of TNFα. This chemical leads to the destruction of the skin and the destruction of the joints. But the exact trigger factors of psoriasis, outside of the genetic factors, all remain to be elucidated.
How can you tell psoriatic arthritis from other types of arthritis?
Psoriatic arthritis can look identical to rheumatoid arthritis. The big difference is that the blood test for rheumatoid factor, which is positive in rheumatoid arthritis, is negative in people with psoriatic arthritis. Osteoarthritis can also look like psoriatic arthritis in the early stages, particularly because they both affect the fingers and toes. There are some X-ray differences, too. Psoriatic arthritis has some very specific X-ray findings, which rheumatoid arthritis and osteoarthritis don''t have. But probably the most important thing when looking for psoriatic arthritis is found on the skin. Obviously, if you have skin involvement, it makes it much more likely that the joint inflammation is caused by psoriasis and not by the other diseases.
How is psoriatic arthritis treated?
If you just have a little mild morning stiffness for 20, 30 minutes then a non-steroidal anti-inflammatory drug (NSAID), such as ibuprofen is fine. If it''s more severe than that, then you can take a drug called methotrexate, which has been used for 20 to 30 years to treat rheumatoid arthritis and psoriasis. The biggest downside of methotrexate, which works well in reducing symptoms, is that it doesn''t prevent the destruction of the joints from continuing. In other words, even though the inflammation may be reduced, the destruction of the joints continues.
Now we also have biologic drugs, and one type is called TNFα blockers. These drugs mop up the excess TNFα in the body. The only one currently approved for psoriatic arthritis is Enbrel* (etanercept); the other biologics, such as Remicade (infliximab) and Humira (adalimumbab), are only approved for rheumatoid arthritis, but they are also being used for psoriatic arthritis.
How effective are biologic treatments?e big difference with these agents versus methotrexate is that these agents prevent the progression of the disease. They appear to stop the destruction in its tracks. These treatments are all extremely effective in people with joint involvement. There are, however, some differences in the way that the skin lesions respond to those different agents. Sometimes higher doses are required to get a matching improvement in the skin disease. But the joint disease improves dramatically with TNFα drugs. What advice do you have for people with psoriasis?
I think the most important message is if you have psoriasis, then at each doctor''s visit, the physician or the patient themselves need to be aware that they have approximately a one in three chance of getting the joint disease. And if a doctor is not asking, the patient has got to be telling the physician about symptoms such as, "I''m waking up with swollen joints. My hands are sore. My knees are stiff for about 30 minutes," so that they can be worked up for possible psoriatic arthritis. The sooner we treat them, the less disability there will be. At the moment, we think about one out of five patients with psoriatic arthritis will eventually be disabled. But if you start treatment early, we should be able to prevent disability in most patients.