Psoriasis is a chronic, recurring disease that causes one or more raised, red patches that have silvery scales and a distinct border between the patch and normal skin.
- A problem with the immune system may play a role, and some people are genetically predisposed to psoriasis.
- Characteristic scales or red patches can appear anywhere on the body in large or small patches, particularly the elbows, knees, and scalp.
- This disease is treated with a combination of exposure to ultraviolet light (phototherapy), drugs applied to the skin, and drugs taken by mouth or given by injection.
Psoriasis is common and affects about 1 to 5% of the population worldwide. Light-skinned people are at greater risk, whereas blacks are less likely to get the disease. Psoriasis begins most often in people aged 16 to 22 years and aged 57 to 60 years. However, people in all age groups and races are susceptible.
The patches of psoriasis occur because of an abnormally high rate of growth of skin cells. The reason for the rapid cell growth is unknown, but a problem with the immune system is thought to play a role. The disorder often runs in families, and certain genes are associated with psoriasis.
Treatment of Psoriasis
- Topical drugs
- Systemic drugs
Topical drugs (drugs applied to the skin) are used most commonly. Nearly everyone with psoriasis benefits from skin moisturizers (emollients).
Other topical agents include corticosteroids, often used together with calcipotriene (also called calcipotriol), which is a form of vitamin D, or coal tar.
Tacrolimus and pimecrolimus are used to treat psoriasis that appears on delicate skin (such as on the face or groin or in skinfolds). Tazarotene or anthralin may also be used.
Very thick patches can be thinned with ointments containing salicylic acid, which make the other drugs more effective.
Many of these drugs are irritating to the skin, and doctors must find which ones work best for each person.
Phototherapy (exposure to ultraviolet light) also can help clear up psoriasis for several months at a time. Phototherapy is often used in combination with various topical drugs, particularly when large areas of skin are involved. Traditionally, treatment has been with phototherapy combined with the use of psoralens (drugs that make the skin more sensitive to the effects of ultraviolet light). This treatment is called PUVA (psoralen plus ultraviolet A).
Many doctors are now using narrowband ultraviolet B (NBUVB) treatments, which are as effective as PUVA. However, NBUVB treatments are done without psoralens and therefore do not have the same side effects, such as extreme sensitivity to sunlight.
Doctors can also treat specific patches of the skin directly by using a laser that focuses ultraviolet light (called excimer laser therapy).
For serious forms of psoriasis and psoriatic arthritis, drugs taken by mouth or given by injection are used. These drugs include cyclosporine, mycophenolate, methotrexate, and acitretin.
Cyclosporine is a drug that reduces the body’s ability to fight infections by suppressing the immune system. Drugs that suppress the immune system are called immunosuppressants. Cyclosporine may cause high blood pressure and damage the kidneys.
Mycophenolate is an immunosuppressant that commonly causes gastrointestinal problems and bone marrow suppression (decreased production of red blood cells, white blood cells, and platelets). It may also increase the risk of lymphoma and other cancers.
Methotrexate decreases inflammation in the body and interferes with the growth and multiplication of skin cells. Doctors use methotrexate to treat people whose psoriasis is severe or does not respond to less harmful forms of therapy. Liver damage and impaired immunity are possible side effects.
Acitretin is particularly effective in treating pustular psoriasis but often raises fat (lipid) levels in the blood and might cause problems with the liver and bones as well as reversible hair loss. It causes severe birth defects and should not be taken by women who may become pregnant. Women should wait at least 2 years after their last dose of acitretin before attempting pregnancy.
People may also be given injections of etanercept, adalimumab, infliximab, alefacept, or ustekinumab, secukinumab, or ixekizumab. These drugs are known as biologic agents. Apremilast is another option and it is taken by mouth. These drugs inhibit certain chemicals involved in the immune system and are called biologic agents. They tend to be the most effective drugs for severe psoriasis, but long-term safety is not clear.