Psoriasis

The red and silvery scales, or plaque, of psoriasis. Source: Wikimedia Commons

Types

• 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.
• Psoriatic arthritis—Joint inflammation that produces symptoms of arthritis in patients who have or will develop psoriasis.

Symptoms

The symptoms of psoriasis vary and depend on the type. Plaque psoriasis, one of the most common forms of psoriasis, is characterized by skin that is red and covered in silver scales. These may crack and bleed when the skin is scratched. The patches can grow in size and merge together, covering large areas. When the fingernails and toenails are involved, there can be discoloration, crumbling, and even detachment of the nail.

These patches or 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.^[1]

Psoriasis on the hand. Source: Wikimedia Commons

Many people with psoriasis experience joint inflammation that produces symptoms of arthritis. This condition is called psoriatic arthritis. Psoriatic arthritis is characterized by pain and swelling in the joints. The National Psoriasis Foundation estimates that between 10% to 30% of people with psoriasis also have psoriatic arthritis.^[2]

Mild psoriasis affects less than 3% of the body surface. Most cases of psoriasis are limited to less than 2% of the skin. Moderate psoriasis covers 3%–10% of the skin. If more than 10% of the body is affected, the disease is considered severe.

The disease may also affect the fingernails, the toenails, and the soft tissues of the genitals and inside the mouth.

Causes

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 about one-third of the 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, then improves. Worsening of symptoms is called a flare-up. Conditions that may cause flare-ups include infections, stress, and changes in climate that dry the skin. Also, certain medicines, including lithium (a mood stabilizer) and beta-blockers (used to treat high blood pressure), may trigger an outbreak or worsen the disease.

Diagnosis

Psoriasis is frequently difficult to diagnose by simply examining the skin because it often looks like other skin diseases. Diagnoses are usually confirmed by examining a small skin sample under a microscope.

Treatment

Psoriasis is usually treated in steps based on the severity of the disease, size of the areas involved, type of psoriasis, and the patient's response to initial treatments.^[3] This is sometimes called the 1-2-3 approach. In step 1, medicines are applied to the skin (topical treatment). Step 2 uses light treatments (phototherapy). Step 3 involves taking medicines by mouth or injection that treat the whole immune system (called 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 (for example, every 12 to 24 months) if a treatment does not work or if adverse reactions occur.

Topical treatment

Topical treatments, or treatments applied directly to the skin, may improve symptoms.^[4] Some patients respond well to ointment or cream forms of corticosteroids, vitamin D3, retinoids, coal tar, or anthralin. Bath solutions and moisturizers may be soothing, but they are seldom strong enough to improve the condition of the skin. Therefore, they usually are combined with stronger remedies.

• Corticosteroids—These drugs reduce inflammation and the turnover of skin cells, and they suppress the immune system. Available in different strengths, topical corticosteroids (cortisone) are usually applied to the skin twice a day. Short-term treatment is often effective in improving, but not completely eliminating, 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. If less than 10% of the skin is involved, some doctors prescribe a high-potency corticosteroid ointment. High-potency corticosteroids may also be prescribed for plaques that don't improve with other treatment, particularly those on the hands or feet. In situations where the objective of treatment is comfort, medium-potency corticosteroids may be prescribed for the broader skin areas of the torso or limbs. Low-potency preparations are used on delicate skin areas.
• Calcipotriene—This drug is a synthetic form of vitamin D3 that can be applied to the skin. Applying calcipotriene ointment twice a day controls the speed of turnover of skin cells. Because calcipotriene can irritate the skin, however, it is not recommended for use on the face or genitals. It is sometimes combined with topical corticosteroids to reduce irritation. Excessive use of calcipotriene may raise the amount of calcium in the body to unhealthy levels.^[5]
• Retinoids—Topical retinoids are synthetic forms of vitamin A. The retinoid tazarotene is available as a gel or cream that is applied to the skin. If used alone, this preparation does not act as quickly as topical corticosteroids, but it does not cause thinning of the skin or other side effects associated with steroids. However, it can irritate the skin, particularly in skin folds and the normal skin surrounding a patch of psoriasis. It is less irritating and sometimes more effective when combined with a corticosteroid. Because of the risk of birth defects, women of childbearing age must take measures to prevent pregnancy when using tazarotene.^[6]
• 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). Coal tar is less effective than corticosteroids and many other treatments and, therefore, is sometimes combined with ultraviolet B (UVB) phototherapy for a better result. The most potent form of coal tar may irritate the skin, is messy, has a strong odor, and may stain the skin or clothing. Thus, it is not popular with many patients.
• Anthralin—Anthralin reduces the increase in skin cells and inflammation. Doctors sometimes prescribe a 15- to 30-minute application of anthralin ointment, cream, or paste once each day to treat chronic psoriasis lesions. Afterward, anthralin must be washed off the skin to prevent irritation. This treatment often fails to adequately improve the skin, and it stains skin, bathtub, sink, and clothing brown or purple. In addition, the risk of skin irritation makes anthralin unsuitable for acute or actively inflamed eruptions.
• 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. Often, it is more effective when combined with topical corticosteroids, anthralin, or coal tar.
• Clobetasol propionate—This is a foam topical medication which has been approved for the treatment of scalp and body psoriasis. The foam penetrates the skin very well, is easy to use, and is not as messy as many other topical medications.
• Moisturizers—When applied regularly over a long period, moisturizers have a soothing effect. Preparations that are thick and greasy usually work best because they seal water in the skin, reducing scaling and itching.

Light therapy

Natural ultraviolet light from the sun and controlled delivery of artificial ultraviolet light are used in treating psoriasis.

• 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. Daily, short, exposure to sunlight that doesn’t burn clears or improves psoriasis in many people. Therefore, exposing affected skin to sunlight is one initial treatment for the disease.
• Ultraviolet B (UVB) phototherapy—UVB is light with a short wavelength that is absorbed in the skin's epidermis (the shallowest layer). An artificial source can be used to treat mild and moderate psoriasis. Some physicians 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. A newer 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 below). It is gaining in popularity because it does help and is more convenient than PUVA. 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 once each week 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. PUVA is normally used when more than 10% of the skin is affected or when the disease interferes with a person's occupation (for example, when a teacher's face or a salesperson's hands are involved). Compared with broadband UVB treatment, PUVA treatment taken two to three times a week clears psoriasis more consistently and in fewer treatments.^[7] 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 for one to two days with UVA-absorbing glasses. Long-term treatment is associated with an increased risk of squamous-cell and, possibly, melanoma skin cancers. Simultaneous use of drugs that suppress the immune system, such as cyclosporine, have little beneficial effect and increase the risk of cancer.
• Light therapy combined with other therapies—Studies have shown that combining ultraviolet light treatment and a retinoid, like acitretin, adds to the effectiveness of UV light for psoriasis. For this reason, if patients are not responding to light therapy, retinoids may be added. UVB phototherapy, for example, may be combined with retinoids and other treatments. One combined therapy program, referred to as the Ingram regime, involves a coal tar bath, UVB phototherapy, and application of an anthralin-salicylic acid paste that is left on the skin for 6 to 24 hours. A similar regime, the Goeckerman treatment, combines coal tar ointment with UVB phototherapy. Also, PUVA can be combined with some oral medications (such as retinoids) to increase its effectiveness.

Systemic treatment

For more severe forms of psoriasis, some patients are prescribed medicines that are taken internally by pill or injection. This is called systemic treatment.

• Methotrexate—Methotrexate (Trexall, Rheumatrex) 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.^[8]
• Retinoids—retinoid, such as acitretin, is a compound with vitamin A-like properties that may be prescribed for severe cases of psoriasis that do not respond to other therapies. Most patients experience a recurrence of psoriasis after these products are discontinued.
• Cyclosporine—Taken orally, cyclosporine (Neoral) 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. The best candidates for this therapy are those with severe psoriasis who have not responded to, or cannot tolerate, other systemic therapies. Its rapid onset of action is helpful in avoiding hospitalization of patients whose psoriasis is rapidly progressing. Cyclosporine may impair kidney function or cause high blood pressure (hypertension). Cyclosporine and methotrexate work by similar mechanisms and have approximately equal effectiveness.^[9]
• 6-Thioguanine—This drug is nearly as effective as methotrexate and cyclosporine. It has fewer side effects, but there is a greater likelihood of anemia. This drug must also be avoided by pregnant women and by women who are planning to become pregnant, because it may cause birth defects.
• Hydroxyurea—Compared with methotrexate and cyclosporine, hydroxyurea is somewhat less effective. It is sometimes combined with PUVA or UVB treatments. Possible side effects include anemia and a decrease in white blood cells and platelets. Like methotrexate and retinoids, hydroxyurea must be avoided by pregnant women or those who are planning to become pregnant, because it may cause birth defects.
• Biologic Response Modifiers—Recently, attention has been given to a group of drugs called biologics, which 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. Some examples are alefacept (Amevive), and etanercept (Enbrel). One agent, efalizumab (Raptiva), was voluntarily removed from the market on April 8,2009 by its manufacturer because of safety concerns. These drugs are injected (sometimes by the patient). Patients taking these treatments need to be monitored carefully by a doctor. Since 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.^[10] Some are approved for adults only.
• Antibiotics—These medications are not used for the routine treatment of psoriasis. However, antibiotics may be prescribed when an infection, such as that caused by the bacteria Streptococcus, triggers an outbreak of psoriasis, as in certain cases of guttate psoriasis.

Combination therapy

There are many approaches for treating psoriasis. Combining various topical, light, and systemic treatments often permits lower doses of each and can result in increased effectiveness. Therefore, doctors are paying more attention to combination therapy.

Living With Psoriasis

People 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.

Psychological support

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.

Research

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. 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). Several of these drugs are awaiting approval by the U.S. Food and Drug Administration (FDA).

Advances in laser technology are making it possible for doctors to experiment with laser light treatment of localized plaques.^[11] A UVB laser was recently tested in a study that was conducted at several medical centers. Although improvements in the skin were noted, this treatment is not without possible side effects. In some patients, the skin became inflamed, blistered, or discolored following treatment.

Prevalence

In the United States, psoriasis affects 2% to 2.6 percent of the population, or between 5.8 and 7.5 million people. Although the disease occurs in all age groups, it primarily affects adults. It appears about equally in males and females.

References

1. ↑ Luba KM, Stulberg DL. Chronic plaque psoriasis. Am Fam Physician. 2006 Feb 15;73(4):636-44. Abstract | Full Text | PDF
2. ↑ Turkiewicz AM, Moreland LW. Psoriatic arthritis: current concepts on pathogenesis-oriented therapeutic options. Arthritis Rheum. 2007 Apr;56(4):1051-66. Review. Citation | Full Text | PDF
3. ↑ Smith CH, Barker JN. Psoriasis and its management. BMJ. 2006 Aug 19;333(7564):380-4. Citation | Full Text | PDF
4. ↑ Federman DG, Froelich CW, Kirsner RS. Topical psoriasis therapy. Am Fam Physician. 1999 Feb 15;59(4):957-62, 964. Abstract | Full Text
5. ↑ Braun GS, Witt M, Mayer V, Schmid H. Hypercalcemia caused by vitamin D3 analogs in psoriasis treatment. Int J Dermatol. 2007 Dec;46(12):1315-7. Citation
6. ↑ Krueger GG, Drake LA, Elias PM, et al.The safety and efficacy of tazarotene gel, a topical acetylenic retinoid, in the treatment of psoriasis. Arch Dermatol. 1998 Jan;134(1):57-60. Abstract | Full Text | PDF
7. ↑ Yones SS, Palmer RA, Garibaldinos TT, Hawk JL. Randomized double-blind trial of the treatment of chronic plaque psoriasis: efficacy of psoralen-UV-A therapy vs narrowband UV-B therapy. Arch Dermatol. 2006 Jul;142(7):836-42. Abstract | Full Text | PDF
8. ↑ Furst DE. The rational use of methotrexate in rheumatoid arthritis and other rheumatic diseases. Br J Rheumatol. 1997 Nov;36(11):1196-204. Abstract | PDF
9. ↑ Heydendael VM, Spuls PI, Opmeer BC, et al. Methotrexate versus cyclosporine in moderate-to-severe chronic plaque psoriasis. N Engl J Med. 2003 Aug 14;349(7):658-65. Abstract | Full Text | PDF
10. ↑ Robinson MR, Korman BD, Korman NJ. Combination immunosuppressive therapies: the promise and the peril. Arch Dermatol. 2007 Aug;143(8):1053-7. Abstract | Full Text | [1]
11. ↑ Zakarian K, Nguyen A, Letsinger J, Koo J. Excimer laser for psoriasis: a review of theories regarding enhanced efficacy over traditional UVB phototherapy. J Drugs Dermatol. 2007 Aug;6(8):794-8. Abstract

Links to Clinical Images

Psoriasis images at Skinsight

Psoriasis images at DermAtlas

Psoriasis images at Hardin MD

Psoriasis images at DermNetNZ

External Links

National Psoriasis Foundation