People with psoriasis have a substantially increased risk for a particular type of joint disease called psoriatic arthritis. This type of arthritis, specific to psoriasis sufferers, causes pain, swelling, and joint destruction in a distinct pattern. Many people also have osteoarthritis (degenerative arthritis, the most common type, comes from the normal wear and tear on the joints over time) or, more rarely, rheumatoid arthritis.
Psoriatic arthritis can have a different set of symptoms and is sometimes treated differently. Approximately 5% to 30% of people with psoriasis will get psoriatic arthritis; the risk of arthritis increases with more extensive skin disease. Research has shown that people with psoriasis are at higher risk for high blood pressure, heart failure, diabetes, depression, alcoholism, and heart attack. One theory is that heart disease may be influenced by inflammation and the amount of inflammation in skin with psoriasis can be substantial.
Psoriatics are also at risk for obesity, which can contribute to the risk of heart disease. Crohn’s disease, a disease of the intestine, is also associated with psoriasis. Skin cancer can also be a side effect, especially for patients who have used light therapy or have taken immunosup-pressing medications such as cyclosporine. This risk appears of be highest for people who have used PUVA treatment for psoriasis.
One recent publication from Great Britain suggested that people with moderate or severe psoriasis have a small but increased lifetime risk of cancers of the blood, such as leukemia and lymphoma. This risk appears to be independent of the type and duration of treatments used for the disease. The lymphoma risk was low but increased for all psoriasis sufferers in this specific group of people with moderate or severe psoriasis, regardless of which treatments they had received.
One other risk of psoriasis is related to the medications used for treatment. All medications have potential side effects, or unwanted effects that can occur in the course of treating psoriasis. In particular, oral, subcutaneous (injected beneath the skin), and intravenous (injected into veins) medications may affect other parts of the body besides the skin. The presence and severity of these effects are usually related to dose level or total amount taken, but can appear unexpectedly at any time.
Most systemic treatments for psoriasis, such as prednisone, cyclosporine, methotrexate, and biologic therapies, work by suppressing the immune system. This medicine-induced immunosuppression puts people at increased risk for new infections or reactivation of old infections. One major concern of sup-pressing the immune system is reactivation of latent tuberculosis.
If a person has been exposed to tuberculosis in the past, whether they know it or not, they may have successfully contained all infection in one location, usually the lung. Immunosuppressive medicines can reduce control of infection and allow tuberculosis to reactivate in the lung or other parts of the body. To minimize this risk, a physician will often do a tuberculosis test called a PPD test and/or a chest x-ray prior to beginning these therapies.