National Organization for Rare Disorders, Inc.

Skip to the navigation


It is possible that the main title of the report Psoriasis is not the name you expected.

Disorder Subdivisions

  • None

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.

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



Fauci AS, et al., eds. Harrison's Principles of Internal Medicine, 14th Ed. New York, NY: McGraw-Hill, Inc; 1998:300-1.

Bennett JC, Plum F, eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, PA: W.B. Saunders Co; 1996:2202-3.


Efalizumab for patients with moderate to severe plaque psoriasis: a randomized controlled trial. JAMA. 2003;290:3073-80.

Gottlieb AB, et al. A randomized trial of etanercept as monotherapy for psoriasis. Arch Dermatol. 2003;139:1627-32.

Gordon KB, McCormick TS. Evolution of biologic therapies for the treatment of psoriasis. Skinmed. 2003;2:286-94.

Weinberg JM. An overview of infliximab, etanercept, efalizumab, and alefacept as biologic therapy for psoriasis. Clin Ther. 2003;25:2487-505.

Rim JH, et al. Positive effects of using calcipotriol ointment with narrow-band ultraviolet B phototherapy in psoriatic patients. Photodermatol Photoimmunol Photomed. 2002;18:131-34.

Iyer S, et al. Etanercept for severe psoriasis and psoriatic arthritis: observations on combined therapy. Br J Dermatol. 2002;146:118-21.

Ellis CN, et al. Cost-effectiveness comparison of therapy for psoriasis with a methotrexate-based regimen versus a rotation regimen of modified cyclosporine and methotrexate. J Am Acad Dermatol. 2002;46:242-50.

Krueger GG. Selective targeting of T cell subsets: focus on alefacept - a remittive therapy for psoriasis. Expert Opin Biol Ther. 2002;2:431-41.

Gottlieb AB, et al. Psoriasis as a model for T-cell-mediated disease: immunobiologic and clinical effects of treatment with multiple doses of efalizumab, an anti-CD11a antibody. Arch Dermatol. 2002;138:591-600.

Tutrone WD, et al. Biologic therapy for psoriasis: a brief history, II. Cutis. 2001;68:367-72.

Barbagallo J, et al. Narrowband UVB phototherapy for the treatment of psoriasis: a review and update. Cutis. 2001;68:345-47.

Faerber L, et al. Cyclosporine in severe psoriasis. Results of a meta-analysis in 579 patients. Am J Clin Dermatol. 2001;2:41-47.

Cowen P. Management of psoriasis. Aust Fam Physician. 2001;30:1033-37.

Feldman S. Advances in psoriasis treatment. Dermatol Online J. 2000;6:4.

Gasparro FP. The role of PUVA in the treatment of psoriasis. Photobiology issues related to skin cancer incidence. Am J Clin Dermatol. 2000;1:337-38.

Sterns RS, et al. Effect of continued ultraviolet B phototherapy on the duration of remission of psoriasis: a randomized study. J Am Acad Dermatol. 1986;15:546-52.


McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). Baltimore. MD: The Johns Hopkins University; Entry No:177990; Last Update:11/7/2003. Available at:

Park R. Psoriasis. eMedicine. Last Updated; September 16, 2003:11pp. Available at:

National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS). Questions and Answers About Psoriasis. May 2003. Available at:


National Psoriasis Foundation

6600 SW 92nd Avenue

Suite 300

Portland, OR 97223-7195

Tel: (503)244-7404

Fax: (503)245-0626

Tel: (800)723-9166



American Autoimmune Related Diseases Association, Inc.

22100 Gratiot Ave.

Eastpointe, MI 48021

Tel: (586)776-3900

Fax: (586)776-3903

Tel: (800)598-4668



NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases

Information Clearinghouse

One AMS Circle

Bethesda, MD 20892-3675


Tel: (301)495-4484

Fax: (301)718-6366

Tel: (877)226-4267

TDD: (301)565-2966



Psoriasis and Psoriatic Arthritis Alliance

P.O. Box 111

St. Albans

Hertfordshire, AL2 3JQ

United Kingdom

Tel: 01923672837

Fax: 01923682606



Genetic and Rare Diseases (GARD) Information Center

PO Box 8126

Gaithersburg, MD 20898-8126

Tel: (301)251-4925

Fax: (301)251-4911

Tel: (888)205-2311

TDD: (888)205-3223


Autoimmune Information Network, Inc.

PO Box 4121

Brick, NJ 08723

Fax: (732)543-7285


European Society for Immunodeficiencies

1-3 rue de Chantepoulet

Geneva, CH 1211


Tel: 410229080484

Fax: 41229069140



AutoImmunity Community



For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see