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Psoriasis is a chronic, inflammatory skin disease. Knees, elbows, scalp, trunk, and nails are the most commonly affected areas. There are several types of psoriasis:
- Plaque—inflamed patches of skin topped with silvery, white scales (most common type)
- Guttate—small, dot-like lesions
- Pustular—weeping lesions and intense scaling
- Inverse (intertriginous)—inflamed patches of skin in body folds (armpits, groin, under breasts)
- Erythrodermic—intense sloughing and inflammation of nearly the entire skin
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The cause of psoriasis is unclear. Signals from a defect in the immune system may result in an overgrowth of skin cells. Because the cells grow faster than they can be shed, they pile up on the skin's surface. The excess skin cells are thought to cause the silvery white scales that are characteristic of plaque-type psoriasis.
Factors that may increase your risk include:
- Family history of psoriasis
- Cold climates
- Certain bacterial infections
- Certain medications, such as beta blockers, tumor necrosis factor-alpha inhibitors, and lithium
- Skin injury
- Suppression of the immune system, including AIDS
The red, thickened, and rough patches of psoriasis may occur anywhere, but are commonly found on the scalp, elbows, knees, palms, and soles. Other symptoms include:
- Silvery white scales
- Pitted or dented fingernails and/or toenails
- Red lesion in folds of skin
- Joint pain suggesting arthritis
The skin may also be sore, burning, or itchy depending on the type of psoriasis.
The rashes may come and go.
You will be asked about your symptoms and medical history. A physical exam will be done. It will include an exam of your skin and nails will be examined. There are no specific blood tests or diagnostic procedures for psoriasis. Sometimes a skin biopsy will be done to confirm the diagnosis.
Treatment is based on:
- The severity of the disease
- The extent and location of the areas involved
- Responsiveness to the treatment
Many patients respond well to treatments applied directly to the skin. Topical treatments include:
- Corticosteroid creams and ointments (most common treatment)
- Synthetic forms of vitamin D and retinoids
- Coal tar preparations
- Bath solutions and moisturizers
- Tacrolimus and pimecrolimus (especially for inverse psoriasis)
Photo (Light) Therapy
If psoriasis covers more than 30% of the body, it is difficult to treat with topical medications alone. Daily, short, nonburning exposure to sunlight clears or improves psoriasis in many people. Sunlight is often included among initial treatments.
A more controlled form of artificial light treatment (UVB phototherapy) is often used in cases that are more widespread. Alternatively, psoriasis can be treated with ultraviolet A (UVA light) and psoralen. Psoralen is an oral or topical medication that makes the body more sensitive to light. This treatment is known as PUVA.
For more severe types of psoriasis, doctors may prescribe a number of other powerful medications, which can be effective, but are associated with side effects that are more serious. These include:
- Methotrexate—a type of systemic medication that affects the whole immune system; should not be taken by pregnant women, women planning to become pregnant, or by their male partners
- Cyclosporine—another type of systemic medication that suppresses the immune system to slow the turnover of skin cells; should not be taken by pregnant or breastfeeding women
- Hydroxyurea—less toxic than methotrexate or cyclosporine, but may be less effective
- Systemic retinoids—Compounds with vitamin A-like properties taken internally may be prescribed in severe cases. Retinoids can cause birth defects, and women must protect themselves from pregnancy for several years after completing treatment. Systemic retinoids are often combined with phototherapy for increased effectiveness and for their property of being protective against squamous skin cancer.
- Newer medications include biologic agents, which affect a part of the body's immune response by targeting certain cells in the immune system that cause inflammation
Avoiding physical trauma to the skin, infections, and cold, dry temperatures may help reduce flare-ups in people with the condition. You may be advised to avoid certain foods if they appear to make your psoriasis worse.
American Academy of Dermatology
National Psoriasis Foundation
Canadian Dermatology Association
Psoriasis Society of Canada
de Prost Y. New topical immunological treatments for psoriasis. J Eur Acad Dermatol Venereol. 2006;20(suppl 2):80-82.
Psoriasis. American Academy of Dermatology website. Available at: https://www.aad.org/dermatology-a-to-z/diseases-and-treatments/m---p/psoriasis. Accessed February 16, 2016.
Moderate to severe psoriasis: biologic drugs. National Psoriasis Foundation website. Available at: https://www.psoriasis.org/about-psoriasis/treatments/biologics. Accessed February 16, 2016.
Moderate to severe psoriasis: systemic medications—methotrexate. National Psoriasis Foundation website. Available at: https://www.psoriasis.org/about-psoriasis/treatments/systemics/methotrexate. Accessed February 16, 2016.
Psoriasis. DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T116742/Psoriasis. Updated September 5, 2016. Accessed September 14, 2016.
Varani J, Bhagavathula N, Ellis CN, Pershadsingh HA. Thiazolidinediones: potential as therapeutics for psoriasis and perhaps other hyperproliferative skin disease. Expert Opin Investig Drugs. 2006;15:1453-1468.
10/2/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: FDA approves new drug to treat psoriasis. US Food and Drug Administration website. Available at: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm183851.htm. Published September 25, 2009. Accessed January 22, 2015.
- Reviewer: Michael Woods, MD
- Review Date: 02/2016
- Update Date: 03/17/2014