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Online version updated November 2012
Questions and Answers about Psoriasis
This booklet contains general information about psoriasis. It describes what psoriasis is, what causes it, and what the treatment options are. If you have further questions after reading this booklet, you may wish to discuss them with your doctor.
What Is Psoriasis?
Psoriasis is a chronic (long-lasting) skin disease of scaling and inflammation that affects greater than 3 percent of the United States population, or more than 5 million adults. Although the disease occurs in all age groups, it primarily affects adults. It appears about equally in males and females.
Psoriasis occurs when skin cells quickly rise from their origin below the surface of the skin and pile up on the surface before they have a chance to mature. Usually this movement (also called turnover) takes about a month, but in psoriasis it may occur in only a few days.
In its typical form, psoriasis results in patches of thick, red (inflamed) skin covered with silvery scales. These patches, which are sometimes referred to as plaques, usually itch or feel sore. They most often occur on the elbows, knees, other parts of the legs, scalp, lower back, face, palms, and soles of the feet, but they can occur on skin anywhere on the body. The disease may also affect the fingernails, the toenails, and the soft tissues of the genitals, and inside the mouth. Although it is not unusual for the skin around affected joints to crack, some people with psoriasis experience joint inflammation that produces symptoms of arthritis. This condition is called psoriatic arthritis.
Individuals with psoriasis may experience significant physical discomfort and some disability. Itching and pain can interfere with basic functions, such as self-care, walking, and sleep. Plaques on hands and feet can prevent individuals from working at certain occupations, playing some sports, and caring for family members or a home. The frequency of medical care is costly and can interfere with an employment or school schedule. People with moderate to severe psoriasis may feel self-conscious about their appearance and have a poor self-image that stems from fear of public rejection and psychosexual concerns. Psychological distress can lead to significant depression and social isolation.
Psoriasis is a skin disorder driven by the immune system, especially involving a type of white blood cell called a T cell. Normally, T cells help protect the body against infection and disease. In the case of psoriasis, T cells are put into action by mistake and become so active that they trigger other immune responses, which lead to inflammation and to rapid turnover of skin cells.
In many cases, there is a family history of psoriasis. Researchers have studied a large number of families affected by psoriasis and identified genes linked to the disease. Genes govern every bodily function and determine the inherited traits passed from parent to child.
People with psoriasis may notice that there are times when their skin worsens, called flares, then improves. Conditions that may cause flares include infections, stress, and changes in climate that dry the skin. Also, certain medicines, including beta-blockers, which are prescribed for high blood pressure, and lithium may trigger an outbreak or worsen the disease. Sometimes people who have psoriasis notice that lesions will appear where the skin has experienced trauma. The trauma could be from a cut, scratch, sunburn, or infection.
Occasionally, doctors may find it difficult to diagnose psoriasis, because it often looks like other skin diseases. It may be necessary to confirm a diagnosis by examining a small skin sample under a microscope.
There are several forms of psoriasis. Some of these include:
- Plaque psoriasis. Skin lesions are red at the base and covered by silvery scales.
- Guttate psoriasis. Small, drop-shaped lesions appear on the trunk, limbs, and scalp. Guttate psoriasis is most often triggered by upper respiratory infections (for example, a sore throat caused by streptococcal bacteria).
- Pustular psoriasis. Blisters of noninfectious pus appear on the skin. Attacks of pustular psoriasis may be triggered by medications, infections, stress, or exposure to certain chemicals.
- Inverse psoriasis. Smooth, red patches occur in the folds of the skin near the genitals, under the breasts, or in the armpits. The symptoms may be worsened by friction and sweating.
- Erythrodermic psoriasis. Widespread reddening and scaling of the skin may be a reaction to severe sunburn or to taking corticosteroids (cortisone) or other medications. It can also be caused by a prolonged period of increased activity of psoriasis that is poorly controlled. Erythrodermic psoriasis can be very serious and requires immediate medical attention.
Another condition in which people may experience psoriasis is psoriatic arthritis. This is a form of arthritis that produces the joint inflammation common in arthritis and the lesions common in psoriasis. The joint inflammation and the skin lesions don’t necessarily have to occur at the same time.
Doctors generally treat psoriasis in steps based on the severity of the disease, size of the areas involved, type of psoriasis, where the psoriasis is located, and the patient’s response to initial treatments. Treatment can include:
- medicines applied to the skin (topical treatment)
- light treatment (phototherapy)
- medicines by mouth or injection (systemic therapy).
Over time, affected skin can become resistant to treatment, especially when topical corticosteroids are used. Also, a treatment that works very well in one person may have little effect in another. Thus, doctors often use a trial-and-error approach to find a treatment that works, and they may switch treatments periodically if a treatment does not work or if adverse reactions occur.
Treatments applied directly to the skin may improve its condition. Doctors find that some patients respond well to ointment or cream forms of corticosteroids, vitamin D3, retinoids, coal tar, or anthralin. Bath solutions and lubricants may be soothing, but they are seldom strong enough to improve the condition of the skin. Therefore, they usually are combined with stronger remedies.
- Topical corticosteroids. These drugs reduce inflammation and the turnover of skin cells, and they suppress the immune system. Corticosteroids are typically recommended for active outbreaks of psoriasis. Long-term use or overuse of highly potent (strong) corticosteroids can cause thinning of the skin, internal side effects, and resistance to the treatment’s benefits.
- Vitamin D analogs. Synthetic forms of vitamin D control the speed of turnover of turnover of skin cells. Excessive use of these creams may raise the amount of calcium in the body to unhealthy levels.
- Retinoids. Topical retinoids are synthetic forms of vitamin A. Because of the risk of birth defects, women of childbearing age must take measures to prevent pregnancy when using retinoids.
- Coal tar. Preparations containing coal tar (gels and ointments) may be applied directly to the skin, added (as a liquid) to the bath, or used on the scalp as a shampoo. Coal tar products are available in different strengths, and many are sold over the counter (not requiring a prescription). The most potent form of coal tar may irritate the skin, is messy, has a strong odor, and may stain the skin or clothing.
- Anthralin. Anthralin reduces the increase in skin cells and inflammation. Doctors may prescribe daily application of anthralin ointment, cream, or paste for brief periods to treat chronic psoriasis lesions. Afterward, anthralin must be washed off the skin to prevent irritation. It discolors skin, bathtub, sink, clothing, and most surfaces.
- Salicylic acid. This peeling agent, which is available in many forms such as ointments, creams, gels, and shampoos, can be applied to reduce scaling of the skin or scalp.
- Clobetasol propionate. This is a foam topical medication, which has been approved for the treatment of scalp and body psoriasis.
- Bath solutions. People with psoriasis may find that adding oil when bathing, then applying a lubricant, soothes their skin. Also, individuals can remove scales and reduce itching by soaking in water containing a coal tar solution, oiled oatmeal, Epsom salts, or Dead Sea salts.
- Lubricants. When applied regularly over a long period, lubricants have a soothing effect. Preparations that are thick and greasy usually work best because they seal water in the skin, reducing scaling and itching.
Natural ultraviolet light from the sun and controlled delivery of artificial ultraviolet light are used in treating psoriasis. It is important that light therapy be administered by a doctor. Spending a lot of time in the sun or a tanning bed can cause skin damage, increase the risk of skin cancer, and worsen symptoms.
- Sunlight. Much of sunlight is composed of bands of different wavelengths of ultraviolet (UV) light. When absorbed into the skin, UV light suppresses the process leading to disease, causing activated T cells in the skin to die. This process reduces inflammation and slows the turnover of skin cells that causes scaling.
- Ultraviolet B (UVB) phototherapy. UVB is light with a short wavelength that is absorbed in the skin’s epidermis. An artificial source can be used to treat mild and moderate psoriasis. Some physicians will start treating patients with UVB instead of topical agents. A UVB phototherapy, called broadband UVB, can be used for a few small lesions, to treat widespread psoriasis, or for lesions that resist topical treatment. This type of phototherapy is normally given in a doctor’s office by using a light panel or light box. Some patients use UVB light boxes at home under a doctor’s guidance.
Another type of UVB, called narrowband UVB, emits the part of the ultraviolet light spectrum band that is most helpful for psoriasis. Narrowband UVB treatment is superior to broadband UVB, but it is less effective than PUVA treatment (see next paragraph). At first, patients may require several treatments of narrowband UVB spaced close together to improve their skin. Once the skin has shown improvement, a maintenance treatment may be all that is necessary. However, narrowband UVB treatment is not without risk. It can cause more severe and longer lasting burns than broadband treatment.
- Psoralen and ultraviolet A phototherapy (PUVA). This treatment combines oral or topical administration of a medicine called psoralen with exposure to ultraviolet A (UVA) light. UVA has a long wavelength that penetrates deeper into the skin than UVB. Psoralen makes the skin more sensitive to this light. Compared with broadband UVB treatment, PUVA treatment taken two to three times a week clears psoriasis more consistently and in fewer treatments. However, it is associated with more short-term side effects, including nausea, headache, fatigue, burning, and itching. Care must be taken to avoid sunlight after ingesting psoralen to avoid severe sunburns, and the eyes must be protected with UVA-absorbing glasses. Long-term treatment is associated with an increased risk of squamous-cell and, possibly, melanoma skin cancers.
For more severe forms of psoriasis, doctors sometimes prescribe medicines that are taken internally by pill or injection. This is called systemic treatment.
- Methotrexate. Like cyclosporine, methotrexate slows cell turnover by suppressing the immune system. It can be taken by pill or injection. Patients taking methotrexate must be closely monitored because it can cause liver damage and/or decrease the production of oxygen-carrying red blood cells, infection-fighting white blood cells, and clot-enhancing platelets. As a precaution, doctors do not prescribe the drug for people who have had liver disease or anemia (an illness characterized by weakness or tiredness due to a reduction in the number or volume of red blood cells that carry oxygen to the tissues). Methotrexate should not be used by pregnant women, or by women who are planning to get pregnant, because it may cause birth defects.
- Retinoids. Oral retinoids are compounds with vitamin A-like properties that may be prescribed for severe cases of psoriasis that do not respond to other therapies. Because these medications also may cause birth defects, women must protect themselves from pregnancy.
- Cyclosporine. Taken orally, cyclosporine acts by suppressing the immune system to slow the rapid turnover of skin cells. It may provide quick relief of symptoms, but the improvement stops when treatment is discontinued. Cyclosporine may impair kidney function or cause high blood pressure (hypertension). Therefore, patients must be carefully monitored by a doctor. Also, cyclosporine is not recommended for patients who have a weak immune system or those who have had skin cancers as a result of PUVA treatments in the past.
- Biologic response modifiers. Biologics are made from proteins produced by living cells instead of chemicals. They interfere with specific immune system processes which cause the overproduction of skin cells and inflammation. These drugs are injected (sometimes by the patient). Patients taking these treatments need to be monitored carefully by a doctor. Because these drugs suppress the immune system response, patients taking these drugs have an increased risk of infection, and the drugs may also interfere with patients taking vaccines. Also, some of these drugs have been associated with other diseases (like central nervous system disorders, blood diseases, cancer, and lymphoma) although their role in the development of or contribution to these diseases is not yet understood. Some are approved for adults only, and their effects on pregnant or nursing women are not known.
Combining various topical, light, and systemic treatments often permits lower doses of each and can result in increased effectiveness. There are many approaches for treating psoriasis. Ask the doctor about the best options for you. Find out:
- How long the treatment may last.
- How long it will take to see results.
- What the possible side effects are.
- What to do if the side effects are severe.
Some individuals with moderate to severe psoriasis may benefit from counseling or participation in a support group to reduce self-consciousness about their appearance or relieve psychological distress resulting from fear of social rejection.
Researchers are trying to learn how skin cells form in order to create healthy skin. At the same time, others are looking at the cells and mechanisms which cause lesions in the skin. If any of these mechanisms can be interrupted, researchers may find a way to stop the disease process.
Significant progress has been made in understanding the inheritance of psoriasis. A number of genes involved in psoriasis are already known or suspected. In a multifactor disease (involving genes, environment, and other factors), variations in one or more genes may produce a greater likelihood of getting the disease. Researchers are continuing to study the genetic aspects of psoriasis, and some studies are looking at the nervous system to determine the genes responsible for the circuitry that causes itching.
Since discovering that inflammation in psoriasis is triggered by T cells, researchers have been studying new treatments that quiet immune system reactions in the skin. Among these are treatments that block the activity of T cells or block cytokines (proteins that promote inflammation). If researchers find a way to target only the disease-causing immune reactions while leaving the rest of the immune system alone, resulting treatments could benefit psoriasis patients as well as those with other autoimmune diseases.
Research has suggested that psoriasis patients may be at greater risk of cardiovascular problems, especially if the psoriasis is severe, as well as obesity, high blood pressure, and diabetes. Researchers are trying to determine the reasons for these associations and how best to treat patients.
More information on research is available from the following websites:
- NIH Clinical Research Trials and You helps people learn more about clinical trials, why they matter, and how to participate. Visitors to the website will find information about the basics of participating in a clinical trial, first-hand stories from actual clinical trial volunteers, explanations from researchers, and links to how to search for a trial or enroll in a research-matching program.
- ClinicalTrials.gov offers up-to-date information for locating federally and privately supported clinical trials for a wide range of diseases and conditions.
- NIH RePORTER is an electronic tool that allows users to search a repository of both intramural and extramural NIH-funded research projects from the past 25 years and access publications (since 1985) and patents resulting from NIH funding.
- PubMed is a free service of the U.S. National Library of Medicine that lets you search millions of journal citations and abstracts in the fields of medicine, nursing, dentistry, veterinary medicine, the health care system, and preclinical sciences.
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
National Institutes of Health
American Academy of Dermatology (AAD)
National Psoriasis Foundation (NPF)
For additional contact information, visit the NIAMS website or call the NIAMS Information Clearinghouse.
The NIAMS gratefully acknowledges the assistance of the following individuals in the preparation and review of the original version of this booklet: Kevin D. Cooper, M.D., University Hospitals of Cleveland/Case Western Reserve University, Cleveland, OH; Gerald Krueger, M.D., University of Utah, Salt Lake City, UT; Mark Lebwohl, M.D., Mount Sinai Medical Center, New York, NY; Laurence H. Miller, M.D., P.A., Chevy Chase, MD; Alan N. Moshell, M.D., NIAMS/NIH; Robert Stern, M.D., Beth Israel Deaconess Medical Center, Boston, MA; and the National Psoriasis Foundation.
The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the U.S. Department of Health and Human Services’ National Institutes of Health (NIH), is to support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases; the training of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. The NIAMS Information Clearinghouse is a public service sponsored by the NIAMS that provides health information and information sources. Additional information can be found on the NIAMS website at www.niams.nih.gov.
For Your Information
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Additional copies of this publication are available from:
National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS)
National Institutes of Health
NIH Publication No. 09–5040