Psoriasis (sore-I-ah-sis) is a common immune-mediated chronic skin disease that comes in different forms and varying levels of severity. Most researchers now conclude that it is related to the immune system (psoriasis is often called an "immune-mediated" disorder).

It is not contagious. In general, it is a condition that is frequently found on the knees, elbows, scalp, hands, feet or lower back. Many treatments are available to help manage its symptoms. More than 4.5 million adults in the United States have it. Between 10 percent and 30 percent of people with psoriasis also develop a related form of arthritis, called psoriatic (sore-ee-AA-tic) arthritis. The National Psoriasis Foundation has gathered the information in this section to help educate people about this complex disease, including its appearance, symptoms and medical and social effects.

What does it look like?

It generally appears as patches of raised red skin covered by a flaky white buildup. In certain kinds of psoriasis, it also has a pimple-ish (pustular psoriasis) or burned (erythrodermic) appearance. Psoriasis can also cause intense itching and burning.

What causes it?

Researchers believe the immune system sends faulty signals that speed up the growth cycle in skin cells.
Watch an animation of the skin growth cycle.

Certain people carry genes that make them more likely to develop psoriasis, but not everyone with these genes develops psoriasis. Instead, a "trigger" makes the psoriasis appear in those who have these genes. Also, some triggers may work together to cause an outbreak of psoriasis; this makes it difficult to identify individual factors.

Possible psoriasis triggers:

• Emotional stress
• Injury to the skin
• Some types of infection
• Reaction to certain drugs

Once the disease is triggered, the skin cells pile up on the surface of the body faster than normal. In people without psoriasis, skin cells mature and are shed about every 28 days. In psoriatic skin, the skin cells move rapidly up to the surface of the skin over three to six days. The body can't shed the skin cells fast enough and this process results in patches also called "lesions" forming on the skin's surface.

How is psoriasis diagnosed?

There is no blood test for psoriasis. Physicians usually diagnose it by examining the affected skin. Less often, a small piece of skin affected by the psoriasis is cut out and examined under a microscope.

Who gets psoriasis?

• Psoriasis is a genetic disease. A family association exists in one out of three cases.
• It often appears between ages 15 and 35, but it can develop at any age.
• About 10 percent to 15 percent of those with psoriasis get it before age 10, and occasionally it appears in infancy.
• Psoriasis is not contagious—no one can "catch" it from another person.

How serious is psoriasis?

Psoriasis is measured in terms of its physical and emotional impact. Physically, if less then 2 percent of the body is involved, the case is considered mild. Between 3 and 10 percent is considered moderate, and more than 10 percent is severe. (The palm of one hand equals 1 percent.) Psoriasis also is measured by its impact on quality of life. When psoriasis involves the hands and feet, it may also be considered severe because of how it affects a person's ability to function. Or, if a person's psychological or emotional well-being is considerably affected, the psoriasis may also be considered severe.

Are there different types of psoriasis?

There are five different types of psoriasis. The most common form of psoriasis is called "plaque psoriasis," which is characterized by well-defined patches of red, raised skin. About 80 percent of people with psoriasis have this type. Plaque psoriasis can appear on any skin surface, although the knees, elbows, scalp, trunk and nails are the most common locations.

The other types of psoriasis are:

Guttate: small, red, individual drops on the skin
Inverse: smooth, dry areas of skin, often in folds or creases, that are red and inflamed but do not have scaling
Erythrodermic: periodic, widespread, fiery redness of the skin
Pustular: involves either generalized, widespread areas of reddened skin, or localized areas, particularly the hands and feet (palmo-plantar pustular psoriasis) Typically, people have only one form of psoriasis at a time. Sometimes two different types can occur together, one type may change to another type, or one type may become more severe. For example, a trigger may convert plaque psoriasis to pustular.
Although the reasons for the changes are not well understood, some triggers may include abrupt withdrawal of medications; an allergic, drug-induced rash that brings on the Koebner response (psoriasis appearing on the site of skin injuries); and severe sunburning.

The different types of psoriasis not only have different appearances, but also may require different types of treatment. It is very important that you talk with your physician about what course of action to take with your type of psoriasis.

What are the most irritating locations for psoriasis?

Scalp: Scalp psoriasis occurs in at least half of all people with psoriasis. It can range from very mild with fine scaling to very severe with thick, crusted plaques.
Genitals: Genital psoriasis acts similar to other affected parts of the body. But because of the sensitivity of the skin, this type may require special considerations.
Hands and Feet: Pustular psoriasis can impair a person's ability to work. Plaque psoriasis can dry out the skin and cause cracking and bleeding.

Nails: Nail changes occur in about half of those with psoriasis and 80 percent of those with psoriatic arthritis. The nails may have small holes (pitting), a changed shape (deformation), separation from the skin (oncholyosis) and discoloration.

What is psoriasis?

Psoriasis is a skin disorder  rather  than  a  disease, where  angry red  lesions  appear  on  the  skin, multiply and results as scales  with  silvery  patches. Ofcourse, it is a over simplification. Sometimes people experience low self-esteem because psoriasis is unsightly and ugly. Psoriasis is often understood  by the public as contagious, which can make social interaction awkward. This may lead to emotional problems such as anxiety, anger, embarrassment and  depression.

There  is  a general  belief  that  psoriasis is an incurable skin  disease. It is estimated  that  four  percent  of  the nation’s  population are affected  with  this  skin  disease. Psoriasis  is  a puzzle  to all physicians  because  the  treatment that works for one victim will have no effect or benefit on another.

How does it occurs?

How does it affect?