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Psoriasis

Definition

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
Psoriasis
Psoriasis
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Causes

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.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition. Risk factors for this condition include:
  • Family history of psoriasis
  • Cold climates
  • Suppression of the immune system, including AIDS
  • Certain bacterial infections
  • Certain medications, such as beta blockers, tumor necrosis factor-alpha inhibitors, and lithium
  • Smoking

Symptoms

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.

Diagnosis

The doctor will ask about your symptoms and medical history. A physical exam will be done including an examination 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

Treatment is based on:
  • The severity of the disease
  • The extent and location of the areas involved
  • Responsiveness to the treatment

Topical Treatment

Many patients respond very 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 ( calcipotriene ointment)
  • Retinoids (tazarotene gel 0.05 and 0.1%)
  • 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.
Phototherapy can be very effective in controlling psoriasis but it requires frequent treatments. It may cause side effects such as nausea, headache, and fatigue, burning, and itching. Both UVB and PUVA may increase the person's risk for squamous cell and, possibly, melanoma skin cancers .

Systemic Treatment

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 medicine 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 medicine 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 diligently 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 medicines include biologic agents, which affect a part of the body's immune response by targeting certain cells in the immune system that cause inflammation, including:
    • Etanercept
    • Adalimumab
    • Alefacept
    • Ustekinumab

Prevention

Avoiding physical trauma to the skin, infections, and cold, dry temperatures may help reduce flare-ups in people with the condition. Your doctor may advise you to avoid certain foods if they appear to make your psoriasis worse.

RESOURCES

National Institutes of Health http://www.nih.gov/

National Psoriasis Foundation http://www.psoriasis.org/

CANADIAN RESOURCES

Canadian Dermatology Association http://www.dermatology.ca/

Psoriasis Society of Canada http://www.psoriasissociety.org/

References

de Prost Y. New topical immunological treatments for psoriasis. J Eur Acad Dermatol Venereol . 2006;20(suppl 2):80-82.

Kasper DL, Braunwald E, Fauci A, Hauser S, Longo D, Jameson JL. Harrison's Principles of Internal Medicine . 16th ed. McGraw-Hill; 2000.

Lebwohl M. Psoriasis. American Academy of Dermatology website. Available at: http://www.aad.org/education/students/psoriasis.htm . Accessed July 15, 2009.

Moderate to severe psoriasis: biologic drugs. National Psoriasis Foundation website. Available at: http://www.psoriasis.org/netcommunity/sublearn03%5Fsevere%5Fbiologics . Accessed October 2, 2009.

Moderate to severe psoriasis: systemic medications—methotrexate. National Psoriasis Foundation website. Available at: http://www.psoriasis.org/netcommunity/sublearn03%5Fsevere%5Fmetho . Accessed October 2, 2009.

Psoriasis vulgaris. DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Updated August 27, 2009. Accessed September 18, 2009.

Tierney LM, McPhee SJ, Papadakis MA. Current Medical Diagnosis and Treatment . 44th ed. McGraw Hill/Appleton & Lange; 2005.

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/what.php : 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 October 2, 2009.

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