Psoriasis is a chronic skin disorder that affects between 5.8 and 7.5 million people in the United States, according to the National Psoriasis Foundation. In psoriasis, new skin cells grow too rapidly, resulting in inflamed, swollen, scaly patches of skin in areas where the old skin has not shed quickly enough. Psoriasis can be limited to a few spots or can involve more extensive areas of the body, appearing most commonly on the scalp, knees, elbows and trunk. Although it is highly visible, psoriasis is not a contagious disease. The cause of psoriasis is unknown, and there currently is no cure.

Psoriasis can strike people at any age, but often appears between the ages of 15 and 25. Likewise, it affects both men and women, with a slightly higher prevalence in women than in men. It is estimated that approximately one-quarter of the people with psoriasis, or between 1.5 and 1.9 million people, are seen by U.S. physicians every year for moderate-to-severe forms of the disease.

This disease can be a physically and emotionally painful condition. It often results in physical limitations, disfiguration and a significant burden in managing the daily care of the disease. Because it is often unattractive and misunderstood by the public, psoriasis also commonly causes sufferers to feel embarrassed, angry, frustrated, fearful, depressed and, in some cases, even suicidal.

Cause of Psoriasis The exact cause of this abnormal skin cell growth in psoriasis is not known. Some researchers believe that a person may be born genetically predisposed to psoriasis, though many people with no apparent family history of the disease are diagnosed each year.

Psoriasis has recently been established as an autoimmune disease, which means that T-cells of the immune system recognize an antigen in the skin and attack the areas where that antigen is found. It is not fully understood what causes this immune response, but it could be triggered by a number of factors such as systemic infections; stress or hormonal changes; injury to the skin (sunburn or surgery incision); alcohol, smoking, obesity and poor diet; and certain medications.

Normally, skin cells (called keratinocytes) undergo a process of growth where they are created and pushed to the surface of the skin, while, at the same time, dead cells are shed from the surface, maintaining a balance. This process of cell birth to death normally takes about 28 days. For people with psoriasis, new cells are created and pushed to the surface in only five days, and dead skin cells cannot be shed fast enough. Excessive skin cells build up and form the scaly lesions that characterize psoriasis.

Types of Psoriasis There are several types of psoriasis, and it is not uncommon for a person to have a combination of different types. Plaque psoriasis (psoriasis vulgaris) is the most common kind of psoriasis. It is characterized by the appearance of red, thick, scaly patches on sites such as the trunk, limbs, elbows, knees and scalp. Several other forms of psoriasis exist, and patients should contact the National Psoriasis Foundation to obtain more information. (NPF: www.psoriasis.org or (800) 723-9166)

Levels of Severity There are various forms of psoriasis, some of which are more or less severe. In general, mild psoriasis means that the disease affects less than three percent of the body's surface area, and moderate psoriasis is defined as affecting three to 10 percent. According to the National Psoriasis Foundation, severe psoriasis affects greater than 10 percent of the body surface area. However, some patients with less than 10 percent of their body surface area affected may still be diagnosed with severe psoriasis if the disease is prevalent in certain areas such as the hands, feet, face or genitals. The palm of one's hand represents approximately one percent of the body's surface.

Although the majority of cases are considered mild, nearly one quarter involve moderate-to-severe forms of the disease. Patients with serious forms suffer a great deal of itching, pain, bleeding and burning sensations. While generally not considered life threatening, psoriasis can be disabling, and as many as 400 people die each year from psoriasis-related causes.

Source: General psoriasis statistics and information provided by the National Psoriasis Foundation (NPF).