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Psoriasis is a chronic, noncontagious skin condition characterized by scaling and inflammation. The inflamed skin forms red, thickened areas with silvery scales. The condition is most commonly found on the scalp, elbows, forearms, knees, shins, ankles, and lower back. The inflammation may also affect the fingernails, toenails, soft tissues of the mouth, genitalia, and joints. The inflamed skin is usually asymptomatic, but may cause pain and discomfort by cracking. Psoriasis is rarely itchy.

Possible Regions of Psoriasis


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The exact cause of psoriasis has not been determined, but current theories suggest that it may be a disorder of the immune system. It appears that T-cells, a type of white blood cell that normally protects the body against infection and disease, trigger inflammation and excessive skin cell reproduction, which causes skin to shed too rapidly. Psoriasis is also believed to be associated with other cellular, biochemical, and metabolic defects.

Psoriasis flare-ups may be triggered by a variety of factors, including environment, certain medications, and stress.

There are five primary types of psoriasis:

Plaque psoriasis: This is the most common form. It is characterized by raised lesions which have a reddened base covered by silvery-white scales. The scales shed frequently and are very dry.

Guttate psoriasis: This type is most often triggered by bacterial infections (most commonly strep throat) and is most common in young adults and children. It is characterized by small, salmon pink drop-like lesions on the trunk, limbs, and scalp. It may clear up by itself after a few weeks or months.

Pustular psoriasis: Blisters of non-infectious pus appear on the skin and may affect large or small areas of the body, most commonly fingers, palms and soles. This type of psoriasis is usually triggered by medications, infections, emotional stress, or certain chemicals. It may be triggered by abrupt withdrawal of systemic steroids.

Inverse psoriasis (also called flexural or intertriginous psoriasis): This is usually found in skin fold areas, such as the armpits, under the breasts, or folds of skin near the genitals or buttocks. It is more likely to be found in people who are overweight and may be exacerbated by friction or sweating in skin fold areas. The plaques are red, smooth, dry and large.

Erythrodermic psoriasis: This is the least common form of psoriasis and is characterized by widespread reddening and scaling of the skin as well as severe itching and skin discomfort. This form occurs after a severe sunburn or use of certain medications.

Some people with psoriasis develop a condition called psoriatic arthritis. This occurs when the inflamed areas of the skin are accompanied by joint inflammation, most often in the hip, spine, knee, or elbow joints but also in the small joints of the hands and feet.

In some cases, psoriasis severely compromises quality of life. In addition to physical discomfort, people with psoriasis may develop emotional problems, such as depression or anxiety, and may experience social difficulties due to visible plaques. If you or a family member is suffering from psoriasis, seek out counseling, support groups, and services.

What are the risk factors for psoriasis?
What are the symptoms of psoriasis?
How is psoriasis diagnosed?
What are the treatments for psoriasis?
Are there screening tests for psoriasis?
How can I reduce my risk of psoriasis?
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What is it like to live with psoriasis?
Where can I get more information about psoriasis?

References:

American Academy of Dermatology website. Available at: http://www.skincarephysicians.com/ .

Gudjonsson JE, Elder JT. Psoriasis: epidemiology. Clin Dermatol . 2007;25(6):535-546.

National Psoriasis Foundation website. Available at: http://www.psoriasis.org/home/ .



Last reviewed November 2013 by Michael Woods, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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