Overview of Psoriasis

Psoriasis is a chronic skin disorder that affects about 2 percent of the population. It is characterized by red, elevated plaques that are often overlaid with thick, silvery white scales. The most commonly affected areas are the elbows, knees, scalp, lower back, and genitalia. Some people have psoriasis on their hands and feet. A condition called inverse psoriasis manifests plaques in folded areas, such as in the armpits and groin.

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While psoriasis can develop at any age, it seems to have two peaks of onset incidence: in the third and sixth decades of life. Psoriasis can be physically and emotionally disabling. This disease is often inherited and carries the potential for causing arthritis (psoriatic arthritis).

Causes of Psoriasis

Although the likelihood for familial transmission may not seem significant, there is a definite genetic predisposition for psoriasis. When one parent is affected, there is roughly a 10 percent risk of a child acquiring psoriasis. The risk rises to almost 50 percent when both parents have psoriasis.

One study analyzing psoriasis in twins found 65 percent of identical twin siblings had psoriasis when the other twin was affected. The exact mode of inheritance is complex and variable. The National Psoriasis Foundation reported that researchers have discovered evidence that psoriasis is an autoimmune disorder.

Most people with psoriasis report that no particular event or illness preceded or brought about their condition, but several well-known triggers include stress, strep infection, and some medications.

Smoking Increases Risk of Psoriasis

Researchers have found that smokers are at increased risk of developing psoriasis. The study appeared in the American Journal of Medicine and looked at 78,532 women over a 14-year period. The heaviest smokers were at the highest risk; quitting reduces the risk slowly, over a period of years.

Publication Review By: Stanley J. Swierzewski, III, M.D.

Published: 31 Aug 2000

Last Modified: 01 Oct 2015