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Synonyms of Psoriasis

  • No synonyms found.

Disorder Subdivisions

  • No subdivisions found.

General Discussion

Psoriasis is a chronic, inflammatory skin disease characterized by dry, reddish (erythematous), thickened patches of skin that are covered with silvery-gray scales. These patches may be referred to as papules or plaques and most often affect the scalp, elbows, knees, hands, feet and/or lower back. The plaques may be intensely itchy (pruritis) or sore. In some cases, individuals with psoriasis may experience abnormalities affecting the fingernails, toenails, and the soft tissues inside the mouth. The severity of psoriasis varies from case to case. Psoriasis may be classified as mild, moderate or severe depending upon the amount of skin involved and the effect on an individual’s quality of life. In approximately one-third of cases a family history of psoriasis is present.


The symptoms of psoriasis range from mild to moderate to severe. In some cases, only a tiny portion of the body may be affected (localized). In other cases, a majority of the body may be affected. Any area of skin of the body may be affected. Symptoms often begin gradually. Recurrent outbreaks tend to vary in frequency and duration according to the severity of the case. There are several distinct forms of psoriasis. The most common form is called plaque psoriasis. Approximately 80 percent of people with psoriasis have this form.

Individuals with plaque psoriasis develop dry, reddish (erythematous), thickened patches of skin that are covered with silvery-gray scales. These patches may be referred to as papules or plaques and most often affect the scalp, elbows, knees and/or the buttocks, although any area of the body may be affected. The papules or plaques may extend and grow together, producing larger plaques in ring or spiral patterns. In some cases, individuals with psoriasis may experience intense itching, discomfort and pain.

Other forms of psoriasis are known as guttate psoriasis, pustular psoriasis, inverse psoriasis, and erythrodermic psoriasis. Guttate psoriasis, also known as eruptive psoriasis, is characterized by the development of numerous, small plaques with silvery scales. The plaques develop rapidly all over the body, usually following a respiratory infection.

Pustular psoriasis is characterized by pus-filled blisters that form on the skin often in clusters. Pustular psoriasis may affect a small area of skin such as the palms or soles or it may cover large areas of skin. Pustular psoriasis may be intensely painful.

Inverse psoriasis, also known as flexural psoriasis, is characterized by the development of large, smooth red patches or plaques on the body’s skin folds (flexion creases) such as the skin under the armpits or breasts or near the genitals and buttocks. Movement or sweating may irritate the affect areas and worsen the condition. The scaling that is common with plaque psoriasis does not occur.

Erythrodermic psoriasis is characterized by widespread reddening and scaling of affected skin often including severe itchiness and pain. Erythrodermic psoriasis is the least common form of psoriasis.

Most affected individuals only experience one form of psoriasis at one time. However, in rare cases, two different forms of psoriasis can affect one person at the same type. In addition, one form can progress to another more serious form.

In approximately 50 percent of cases of psoriasis nail abnormalities are present. Nail abnormalities may include malformation, thickening or discoloration of the nails (onychodystrophy); holes in the nails (pitting); or loosening or separation of the nails from the nail bed. In some cases, psoriasis will affect only the nails and no other part of the body.

In some case, the soft tissues inside the mouth or around the genitals may also be affected. Approximately, 10 to 30 percent of individuals with psoriasis develop inflammation and pain of certain joints, a condition known as psoriatic arthritis. (For more information on this condition, see the Related Disorders section below.)


The exact cause of psoriasis is unknown. A family history is present in approximately one-third of cases of psoriasis meaning that certain individuals may have a genetic predisposition for the disorder. A genetic predisposition means that a person may carry a gene or genes for a disease but it may not be expressed unless something in the environment triggers the disease. It is believed that multiple defective genes in association with certain environmental factors cause the development of psoriasis in these cases.

Researchers believe that psoriasis is a disorder of the immune system (an immune-mediated or autoimmune disorder). When foreign substances invade the body, the immune system produces various cells and chemicals to combat the invading organisms or infection. One of the key components of the immune system is a type of white blood cell known as a T-lymphocyte or T-cell. In individuals with psoriasis, the immune system mistakenly produces T-cells, which causes additional unnecessary immune system responses. This abnormal activity of the immune system results in excessive production of skin cells.

Researchers have identified a gene that plays a role in the development of psoriasis. Named the psoriasis susceptibility 1 (PSORS1) gene, it is located on chromosome 6 and is involved in how the immune system fights off infection. Chromosomes, which are present in the nucleus of human cells, carry the genetic information for each individual. Pairs of human chromosomes are numbered from 1 through 22, and an additional 23rd pair of sex chromosomes which include one X and one Y chromosome in males and two X chromosomes in females. Each chromosome has a short arm designated "p" and a long arm designated "q". Chromosomes are further sub-divided into many bands that are numbered.

Researchers believe the excessive production of skin cells causes the inflammation and scaling that is characteristic of psoriasis. Skin cells normally rise from beneath the skin where they are formed to the surface of the skin (a process known as turnover). As new skin cells turnover, old ones are shed. In individuals with psoriasis, the excessive production of new skin cells causes too many skin cells to turnover before enough old ones are shed. The new skin cells then abnormally accumulate on the surface of the skin resulting in inflammation and scaling.

In some cases, certain substances referred to as triggers may worsen the symptoms of psoriasis in affected individuals. Triggers include changes in climate, infections, physical trauma, emotional and physical stress, and certain medications.

Affected Populations

Psoriasis affects males and females in equal numbers. It occurs in approximately 2 percent of the population of the United States, about five million people. Psoriasis most often affects individuals between the ages of 15 to 35, but it can occur at any age. Approximately 10 percent to 15 percent of cases of psoriasis occur in children under the age 10. Psoriasis is not contagious.

Related Disorders

Symptoms of the following disorders can be similar to those of psoriasis. Comparisons may be useful for a differential diagnosis:

Pityriasis rubra pilaris is a mildly itchy chronic skin disorder. Initially, the disorder is characterized by elevated spots (papules) on the skin that grow and become connected, producing red plaques over large areas. These papules usually occur on the back of the wrists, the outside of the forearms, underarm folds, elbows, knees, backs of the hands, and fingers. When the papules grow and connect together they produce dry, scaly, rough, red plaques over large areas of the skin. The exact cause of pityriasis rubra pilaris is unknown. An acquired and an inherited form of the disorder have been reported in the medical literature. (For more information on this disorder, choose "pityriasis rubra pilaris" as your search term in the Rare Disease Database.)

Lichen planus is a rare, recurrent, itchy rash or area of inflammatory eruptions (lesions) of unknown origin characterized by shiny reddish-purple spots on the skin and gray-white ones in the mouth. The disorder may present as itchy spots on the wrist, legs, torso, genitals, mouth, or lips. The eruptions may appear as small separate, angular spots that may coalesce into rough scaly patches. This disorder is frequently accompanied by oral lesions of the mucous membranes that line the mouth. The disorder affects women more frequently than men. The exact cause of lichen planus is unknown. (For more information on this disorder, choose "Lichen Planus" as your search term in the Rare Disease Database.)

Pityriasis rosea is a self-limited, mild, inflammatory skin eruption characterized by scaly lesions found most commonly on the trunk. The disorder is possibly due to an unidentified infectious agent. It may occur at any age but is seen most frequently in young adults. In temperate climates, incidence is highest during the spring and autumn.

Parapsoriasis are a rare group of chronic skin disorders characterized by the development of rounded, reddish (erythematous), scaly papules. The skin conditions that make up parapsoriasis have a strong resemblance to psoriasis, but are clinically distinct disorders. There is significant debate in medical literature as to specific definition of what is parapsoriasis. Some researchers believe that parapsoriasis is an early form of mycosis fungoides, a form of cutaneous T-cell lymphoma. The exact cause of parapsoriasis is unknown.

The following disorder may be associated with psoriasis as secondary characteristics. It is not necessary for a differential diagnosis:

Psoriatic arthritis is a rheumatoid-like arthritic condition characterized by pain and swelling (inflammation) of the joints (arthritis) that occurs in association with gray discoloration or scaly plaques of the skin (psoriasis). Abnormalities of the nails may also be present. In many cases, skin symptoms precede the development of arthritis by several years. The exact cause of the psoriatic arthritis is unknown. (For more information on this disorder, choose "psoriatic arthritis" as your search term in the Rare Disease Database.)

Standard Therapies

A diagnosis of psoriasis is made based upon a detailed patient history and a thorough clinical evaluation in which the skin is examined. In some cases, a diagnosis may be confirmed by surgical removal and microscopic examination (biopsy) of a small sample of affected skin.

The treatment of psoriasis depends upon the specific type of psoriasis present, the severity of the disease, and an affected individual’s age, general health, and specific response to various treatment options. The three main ways psoriasis is treated are: administering medications applied directly to the skin (topical therapy); using light therapy (phototherapy); and prescribing drugs that target or treat the entire immune system (systemic therapy).

Topical forms of certain medications are usually the initial treatment for individuals with psoriasis. Such medications include corticosteroids; synthetic forms of vitamin D such as calcipotriene (Dovonex); synthetic forms of vitamin A (retinoids) such as tazarotene (Tazorac); and additional drugs such as anthralin. Topical therapies for psoriasis also include salicylic acid and crude coal tar.

Additional topical therapies include lubricating creams; hydrogenated vegetable oils; or white petroleum jelly (e.g. Vaseline), which are applied alone or combined with corticosteroid drugs, salicylic acid, crude coal tar, or anthralin while the skin is still damp after bathing. Alternatively, crude coal tar ointment or cream may be applied at night and washed off in the morning, followed by exposure to natural or artificial (280 to 320 nm) ultraviolet light in slowly increasing amounts. Anthralin can be effective as an ointment applied carefully to the lesions under a dressing that does not seal off the lesion completely at bedtime. It should be removed in the morning with mineral oil. Anthralin may be irritating and should not be used in folds of the skin such as the neck, armpit and groin. Anthralin stains sheets and clothing as well as the skin. Local corticosteroid drugs may be used as an alternative or in combination with anthralin or coal tar treatment.

Corticosteroid creams such as triamcinolone acetonide are most effective when used overnight with waterproof plastic coverings or impregnated in adhesive tape. A corticosteroid cream may be applied without a plastic covering during the day. If potent fluorinated corticosteroids are applied to large areas of the body, especially under a plastic covering, psoriasis may be aggravated as with systemic corticosteroids. For small, localized lesions, fluorandrenolide-impregnated tape left on overnight and changed in the morning is usually effective. Relapses may occur after application of local corticosteroids more quickly than with other treatments. Thick scalp plaques may be more difficult to treat. A preparation containing an oily solution of phenol and sodium chloride, or salicylic acid in mineral oil may be rubbed in at bedtime with a toothbrush and washed out the next morning with a detergent shampoo. A shower cap can be worn in bed to enhance penetration and to avoid staining. Tar-containing shampoos are often used. Local corticosteroid lotions or gels may be applied during the day. Resistant skin or scalp patches may respond to local injections of a suspension of the glucocorticoid drug, triamcinolone acetonide diluted with saline solution. However, these injections may cause local tissue shrinkage.

Phototherapy is used for individuals with mild, moderate or severe psoriasis or individuals who do not respond to topical therapy. Phototherapy may be administered by itself or in conjunction with topical treatments. Mild psoriasis may be treated by greater exposure to sunlight. Mild to moderate psoriasis may be treated by a procedure in which the skin of affected individuals is exposed to ultraviolet B (UVB phototherapy). Psoralens and ultraviolet A (PUVA) is used to treat individuals with severe psoriasis. The sun-protecting drug methoxsalen (a psoralen compound) in oral form is followed by exposure of the skin to long-wave ultraviolet light under supervision of a dermatologist. This therapy may produce remissions for several months, but long-term, repeated treatments may cause skin cancer in some cases.

Systemic therapies used to treat psoriasis include methotrexate and cyclosporine; biologic therapies such as alefacept or efalizumab; and oral retinoids. The cancer-fighting drug methotrexate, taken orally, is the most effective treatment in the most severe cases of psoriasis that are unresponsive to other available therapies. Methotrexate seems to interfere with the rapid growth of skin cells. Because the potential toxicity requires careful monitoring of blood, kidney and liver function, and because dosage regimens vary, methotrexate therapy should be carefully monitored by physicians experienced in its use for psoriasis.

The immunosuppressive drug cyclosporine (Sandimmune) is used for short-term treatment of severe psoriasis that has not responded to other standard therapies such as UVB light treatment, methotrexate or etretinate. Cyclosporine suppresses the immune system, so long-term use and/or high dosage can make a person vulnerable to other disorders.

Alefacept (Amevive), a systemic biologic therapy, was approved by the Food and Drug Administration (FDA) in January 2003 for treatment of moderate to severe psoriasis in adults who are candidates for systemic therapy or phototherapy. For information on Amevive, contact:

14 Cambridge Center
Cambridge, MA 02142
Telephone: (617) 679-2000
Fax: (617) 679-2617

Efalizumab (Raptiva), a systemic biologic therapy, was approved by the FDA in December 2003 for the treatment of moderate to severe psoriasis. In clinical trials, treatment with efalizumab reduced the frequency and severity of symptoms associated with psoriasis. For more information on Raptiva, contact:

1 DNA Way
South San Francisco, CA
Phone: (650) 225-1000
Fax: (650) 225-6000

Genetic counseling may be of benefit for affected individuals and their families. Other treatment is symptomatic and supportive.

Investigational Therapies

Information on current clinical trials is posted on the Internet at All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

For information about clinical trials being conducted at the National Institutes of Health (NIH) Clinical Center in Bethesda, MD, contact the NIH Recruitment Office:

Tollfree: (800) 411-1222
TTY: (866) 411-1010

For information about clinical trials sponsored by private sources, contact:

The retinoid drug etretinate (Tegison) has been used in Europe in the treatment of psoriasis, especially the pustular type, and in psoriasis of the hands and feet. More research is necessary to establish effectiveness and safety of retinoid drugs as a treatment for Psoriasis. The drug hull24, previously called anti-CD11a, has received an orphan drug designation for its use in the treatment of psoriasis. More studies are needed to determine the long-term safety and effectiveness of this drug for the treatment of this disease. For more information, contact: XOMA Corp. 2910 Seventh St Berkeley, CA 94710 (415) 644-1170

Researchers are studying infliximab (Remicade), a monoclonal antibody, as a potential treatment for individuals with moderate-to-severe psoriasis. Initial studies have demonstrated significant improvement in symptoms. More research is necessary to determine the long-term safety and effectiveness of infliximab for the treatment of psoriasis.

According to the medical literature, etanercept has been used to treat individuals with severe psoriasis and psoriatic arthritis. Etanercept was given to affected individuals in combination with an existing treatment regimen and resulted in marked improvement of symptoms. Etanercept has also been studied in clinical trials as a lone therapy for psoriasis (monotherapy). Initial results demonstrated that etanercept monotherapy resulted in significant improvement of symptoms in individuals with psoriasis. More research is necessary to determine the safety and effectiveness of this potential treatment for cases of severe psoriasis.

Additional therapies being studied as potential treatments for psoriasis include hydroxyurea, mycophenolate motefil, sulfasalazine, and 6-Thioguanine. More research is necessary to determine the long-term safety and effectiveness of these treatments for individuals with psoriasis

Psoriasis Resources

NORD Member Organizations:

(To become a member of NORD, an organization must meet established criteria and be approved by the NORD Board of Directors. If you're interested in becoming a member, please contact Susan Olivo, Membership Manager, at

Other Organizations:


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The information in NORD’s Rare Disease Database is for educational purposes only. It should never be used for diagnostic or treatment purposes. If you have questions regarding a medical condition, always seek the advice of your physician or other qualified health professional. NORD’s reports provide a brief overview of rare diseases. For more specific information, we encourage you to contact your personal physician or the agencies listed as “Resources” on this report.

Report last updated: 2008/05/12 00:00:00 GMT+0

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