Psoriasis Overview
Psoriasis is a chronic, noncontagious skin disease characterized by red patches of skin often accompanied by silvery-white scales of dead skin ...

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Psoriasis is a chronic skin disease characterized by red patches on the skin, often accompanied by silvery-white scales of dead skin cells. It is not contagious.

Psoriasis is believed to be an autoimmune disease, meaning the body’s defense system attacks healthy cells in the body. This creates skin cells that mature and die in less than a week, which is extremely rapid considering normal skill cells mature and replace dead ones usually in a month’s time.

The buildup of dead cells on the skin’s surface is called plaque. While these can occur anywhere on the body, they are more common in the following areas:

  • hands
  • elbows
  • legs
  • back
  • chest
  • fingernails
  • toenails
  • scalp
  • folds in the buttocks and groin 

The National Psoriasis Foundation estimates that as many as 7.5 million Americans and 125 million people worldwide (about 2.2 percent of the population) have psoriasis, making it the most prevalent autoimmune disease in the world.

While psoriasis affects the skin, it goes beyond a cosmetic problem. The exterior symptoms of psoriasis can affect a person’s self-esteem and personal image, which can create problems in their everyday lives such as anxiety and alienation.

Types of Psoriasis

There are several different types of psoriasis, distinguished by 1) the affected area of the body and 2) the type of patches. They include:

Scalp Psoriasis

This type involves plaques on the scalp that typically can be confused as dandruff. About half of all people with any type of psoriasis also have scalp psoriasis.

Plaque Psoriasis

Found anywhere on the body, plaque psoriasis is the most common form of psoriasis. Small red bumps spread and dead skin cells easily flake from those areas.

Inverse Psoriasis

This type of psoriasis involves smooth inflamed lesions in areas where the skin folds or flexes, such as the armpits, groin, or under the breast.

Erythrodermic Psoriasis

This kind causes severe disruption to the body’s chemical balance, affecting the majority of the body, and causes symptoms such as severe scaling, pain, and itching to the point where the skin looks as though it has been burned. It can also cause severe illness.

Pustular Psoriasis

Characterized by puss-filled blister-like lesions, this kind can be contained to a small area or widespread. It can be a precursor to plaque psoriasis or develop in those who already have it.

Palmar-plantar Pustulosis

A type of pustular psoriasis, it causes pustules to form at the sides of the heel or base of the thumb that turn brown and peel.

Guttate Psoriasis

This involves small, red dots that enlarge rapidly and often develop scales in the scalp, arms, legs, and torso. They can clear up without any treatment, but may appear later as plaque psoriasis. 

Nail Psoriasis

This form of psoriasis affects the fingernails and toenails with pitting, discoloration, flaking, or possible separation from the nail bed.

Complications and Considerations

People with psoriasis run a larger risk of developing psoriatic arthritis, a type of joint swelling and inflammation associated with psoriasis. The immune system attacks joints the same way it attacks healthy skin cells, causing joint swelling, tenderness, and pain. Psoriatic arthritis is often slow to develop, but it can develop rapidly, often in conjunction with severe skin outbreaks.

If your psoriasis gets suddenly worse—that is, you begin experiencing increased pain, swelling, and tenderness; develop red, radiating streaks around the psoriasis patch; notice a discharge or pus; have side effects such as vomiting, bloody diarrhea, chills, or begin running a fever over 100.4°F—you should call your doctor’s office immediately. If he is not in or cannot see you, asked to be referred to another doctor who can provide you with immediate medical attention. Your condition may be worsening and need quick attention.

Written by: the Healthline Editorial Team
Edited by:
Medically Reviewed by: Jennifer Monti, MD, MPH
Published: Jun 10, 2011
Published By: Healthline Networks, Inc.
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