Psoriasis Skin Disorder
Psoriasis is a chronic skin disorder affecting more than 4 million individuals, producing silvery, scaly plaques on the skin. The skin condition usually begins in adolescence and affects 2 percent of the population. The most common type of psoriasis is called “plaque psoriasis” (or psoriasis vulgaris), characterized by raised, inflamed lesions with silver-white scales. Other far less common forms include pustular, guttate, inverse, and erythrodermic psoriasis.
The condition is considered to be mild if only 10 percent or less of the body is affected; 10 percent to 30 percent indicates a moderate problem, and psoriasis over more than 30 percent of the body is considered to be severe. The location of the symptoms, more than the extent, influences how disabling the condition may be. Psoriasis only on the palms and soles of the feet can be physically disabling, while psoriasis on the face can be emotionally disturbing. Typically, a person with psoriasis experiences cycles of improvement and flares; the disease can go into remission for periods ranging from one to 60 years.
What causes Psoriasis?
The cause of psoriasis is unknown, although researchers believe that some type of biochemical stimulus triggers the abnormal cell growth in the skin. While normal skin cells take a month to mature, patients with psoriasis have skin cells that over-multiply, forcing the cells to move up to the top of the skin in only seven days. As the number of cells builds up, the skin thickens and the extra cells accumulate in raised, red, and scaly lesions.
The white scales covering the red lesions are made up of dead cells that are continually shed; the inflammation is caused by the buildup of blood needed to feed the rapidly dividing cells. Skin trauma, emotional stress, and some kinds of infection may trigger the development of psoriasis. The condition sometimes forms at the site of a surgical incision or after a drug reaction. While anyone can develop psoriasis, there appears to be a hereditary link and a family association in one out of three cases.
It is not known whether just one gene, or a collection, predisposes a person to the condition, but it is believed that one gene modified by others in combination with certain environmental factors produces psoriasis. This may be why there is not one pattern of inheritance from one generation to the next. Both boys and girls can develop psoriasis at any age, but most patients develop lesions between ages 10 and 35, although a few may contract the disease in infancy or early childhood. Certain races seem more susceptible to developing the condition. Caucasians have the highest percentage, although East Africans are also at risk. African Americans have a low incidence of the disease.
Symptoms of Psoriasis
The first lesions of plaque psoriasis appear as red, dotty spots that can be very small; these eruptions slowly get larger, producing a silvery white surface that is shed easily. When forcibly removed, the scales may leave tiny bleeding points. The plaques, which often appear in the same place on the right and left sides of the body, often cover large areas of skin, merging into one another. The most common sites are scalp, elbows, knees, and trunk, although they can be found anywhere on the body. Lesions vary in size and shape from one person to the next, and patches spread over wide expanses of skin can lead to intense itching, pain, dry or cracking skin, and swelling. Body movement and flexibility may be affected.
Potentially more disabling than the physical discomfort is the emotional impact of a disfiguring disease that can produce lack of self-confidence, depression, guilt, or anger. About 10 percent of patients develop psoriatic arthritis, causing inflammation and stiffness.
Diagnosis
Psoriasis is usually diagnosed by observation. There are no blood tests for the disease, although doctors sometimes examines a skin biopsy under a microscope to confirm the diagnosis. Sometimes small pits in the fingernails, yellow discoloration of the nail, or collections of scaly skin under the nail can help diagnose the condition.
Psoriasis Treatment
There is no cure for psoriasis, but there are treatments that can clear plaques or significantly improve the skin’s appearance. Treatment is aimed at slowing the excessive skin division, resulting in remissions lasting up to a year or more. Once the treatment is effective, it is discontinued until the psoriasis returns. Type of treatment depends on the type of psoriasis, its location and severity, patient age, and patient medical history. Dermatologists usually begin with the mildest therapy and work up to the one that is most effective in clearing up the skin problem. No single treatment works for everyone, and each patient reacts differently to the drugs.
Topical medications (emollients, steroids, vitamin D derivatives, anthralin, and coal tar preparations) are used to treat mild to moderate conditions. These may be used alone or in combination with each other, or with ultraviolet light treatments. Regular sunbathing may help clear up a case of psoriasis for some patients because of the exposure to natural ultraviolet-B light. For more severe cases, the topical treatments above will be combined with psoralen plus UVA, chemotherapy (methotrexate), and oral retinoid medications such as Tegison. Treatments for severe psoriasis are toxic and must be weighed against their potential benefits and risks.
In a new treatment for localized psoriasis, a laser is used to target small plaques. The laser produces high-intensity UVB light at the wavelengths most effecting for clearing psoriasis. Because the light is so intense and the laser can be aimed just at the affected spot, clearing can occur in just six to eight treatments. Cleared areas may remain clear for six to eight months.
On the Horizon
More than 40 experimental drugs are being tested for the treatment of psoriasis and/or psoriatic arthritis. Some of the drugs now in testing represent attempts at improving existing therapies, but many of the innovative drugs are pursuing treatment in a new way, by targeting the immune system’s role in psoriasis. A promising drug in development is Xanelim (developed by Genentech and XOMA). This drug represents the front line of a new generation of psoriasis therapies: biologically engineered drugs that target a very specific part of the immune reaction that takes place in psoriasis.
These “biologics,” as they are called, hold the promise of being as effective as today’s most potent psoriasis treatments but much safer and with fewer side effects. These new treatments target and block specific parts of the body’s immune reaction that leads to the diseases. However, they are still under investigation and are not yet approved for psoriasis patients by the U.S. Food and Drug Administration (FDA).
Amevive (alefacept) and Raptiva have both been approved by the FDA. Amevive (alefacept), an injected medication that treats adults with moderate to severe plaque psoriasis, was approved by the FDA in January 2003. Experts believe Amevive works by simultaneously blocking and reducing the cellular component of the immune system that is thought to play a significant role in the disease process. FDA based its approval of Amevive on the results of two studies of 1,060 adults with chronic plaque psoriasis. Both of these studies showed that a significantly higher percentage of patients receiving Amevive responded to treatment compared to those receiving placebo. In the approved labeling for Amevive, FDA is encouraging physicians to tell patients that they need regular monitoring of white blood cell counts during therapy.
The approved labeling states that patients should be told that Amevive suppresses their immune system, which could increase their chances of developing an infection or malignancy. This means that patients should tell their doctor promptly if they develop any signs of an infection or malignancy during treatment. Females of childbearing age make up a considerablesegment of the patient population affected by psoriasis, but no one knows of the effect of Amevive on pregnancy and fetal development, including immune system development. Phase III trials of the drug Xanelim were promising, but it may be several years before the drug is submitted to the FDA for approval.
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