Last reviewed by Faculty of Harvard Medical School on January 24, 2013
By Harvey B. Simon, M.D.
Harvard Medical School
Psoriasis is an old disease. In fact, its very name comes from an ancient Greek word meaning an itchy or scaly condition.
About 7 million Americans are plagued by this itching and scaling. Many of them have serious complications involving internal organs. Psoriasis is a chronic condition. It affects both males and females at any time from childhood to old age. It ranges from mild to severe. In general, the earlier it starts, the more likely it is to involve large areas of skin and to have serious consequences.
Although psoriasis is classified as a dermatologic disease, it doesn't start in the skin, and its damage may be more than skin deep.
What Happens In Psoriasis?
At a basic level, psoriasis is a disorder of the immune system. White blood cells called T lymphocytes become overactive. They produce excess amounts of chemicals called cytokines. In turn, these chemicals trigger inflammation in the skin and other organs.
In the skin, the inflammation causes widened blood vessels, an accumulation of white blood cells, and an abnormally rapid increase in keritinocytes the main cells in the outer layer of the skin. In healthy skin, keritinocytes take about a month to divided, mature, migrate to the skin surface, and slough off to make way for younger cells. But in psoriasis, the entire process is speeded up, and takes place in as few as three to five days. The result is thickened, red skin that sheds silvery scales of keritinocytes that have matured before their time.
Why does the immune system veer off target in psoriasis? In about a third of cases it's due to genetics. Psoriasis runs in families. There are at least nine abnormal genes associated with psoriasis, and more are likely to be discovered.
But environmental factors also play a role. Psoriasis has been linked to psychological stress, obesity, smoking, alcohol, strep throat, viral infections, lack of sunlight and certain medication (anti-malaria drugs, lithium, beta-blockers, and others).
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Types of Psoriasis
Psoriasis comes in many forms.
About 90% of patients have the plaque type with its sharply defined, salmon-pink plaques of inflamed skin covered by silvery scales. In most cases, the plaques develop symmetrically on both sides of the body. Plaques are most common on the:
- Scalp, especially at the hairline
- Crease between the buttocks
- Palms and soles
- Ear canals
- "Belly button"
About half of all patients with plaque psoriasis have nail involvement. Some people have nail psoriasis without skin inflammation. Nail problems range from tiny pits to yellowing of the nail surface and accumulation of debris under the nails. Nail psoriasis is often linked to arthritis (see below).
This is the second most common from of the disease. Latin scholars have a head start in understanding this variety, because the name comes from "gutta," meaning droplet.
Patients have many small red scaly spots scattered on the arms and legs. In children and adolescents, gluttate psoriasis can develop abruptly several weeks after a strep throat or viral infection. When this happens, it can resolve on its own in three to four months, but it may also convert to plaque psoriasis.
These common forms of psoriasis may be mild, but they may also be very distressing. Itching is troublesome, but the unsightly skin changes can cause even more unhappiness, especially when large areas of skin are involved and scales accumulate on clothing and furniture.
Other forms of the disease are much more serious. These include one type that causes severe inflammation of the entire skin surface. Another can look as if there are a huge number of small boils all over the body. Fortunately, these life-threatening forms of psoriasis are rare.
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Psoriasis can damage internal organs and structures. That's because immune system abnormalities cause the disease.
Arthritis Up to 25% of patients with psoriasis develop joint inflammation. In some cases, the arthritis can come on before the skin involvement. There is a strong link between nail psoriasis and arthritis; some arthritis patients have nail disease without any skin inflammation.
Psoriatic arthritis can strike the small joints of the fingers, one or two larger joints elsewhere in the body, or the spine. It is a painful, chronic inflammatory arthritis, but tests for rheumatoid arthritis and other forms of auto-immune arthritis are negative. Some patients improve with non-steroidal anti-inflammatory drugs. Others patients need powerful medications to quiet down the immune system.
Cardiovascular disease New research has established a link between psoriasis and heart attacks. Patients who developed severe psoriasis at a relatively young age have the highest risk of cardiovascular complications. The link does not depend on risk factors that both psoriasis and heart disease have in common, such as smoking, obesity and stress. Instead, researchers believe that inflammation is the thread that ties psoriasis to artery disease.
Psychosocial disorders Like other chronic diseases, psoriasis can cause emotional distress and disrupt a person's relationships and ability to work. Physical discomfort and disfigurement combine to make severe psoriasis a disabling disease.
Other conditions Patients with psoriasis have an increased risk of diabetes, high blood pressure, Crohn's disease (a type of bowel inflammation) and other conditions. Patients who receive aggressive therapy may also have a high risk of certain cancers.
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People with very mild psoriasis may be able to get help from things as simple as a skin moisturizer, an anti-dandruff shampoo and some sunlight. But most patients require medically supervised therapy. Although no treatment will cure psoriasis, many medications can control the disease.
Prescription ointments, gels or lotions are the mainstay of treatment, especially for mild-to-moderate disease. In the past, coal tar and anthralin were widely recommended. But they stained skin and clothing. So they have been replaced by topical treatments that are more convenient and more effective. Corticosteroid preparations of different strengths are available. They all reduce inflammation and control itching. Corticosteroids act rapidly, but long-term use of strong steroids can thin and damage skin. Newer topical therapies are proving very effective. These include include calcipotriene (Dovonex), a vitamin D derivative, and tazarotene (Tazorac), a relative of vitamin A. Both are prescription drugs.
At one time, phototherapy (light therapy) involved two to four weeks of sunbathing, referred to as "climatotherapy." Some people could afford getting naturally filtered sunlight at the Dead Sea. Now, though, doctors use carefully controlled exposure to ultraviolet (UV) radiation to treat moderate-to-severe psoriasis. UVB can be administered alone or in combination with tar or other topical agents. UVA is usually reserved for extensive psoriasis that has not improved with other treatments. It is used along with a light-sensitizing drug as part of the PUVA regimen.
The toughest cases of psoriasis call for the toughest treatments. These include the oral vitamin A-like drug acitretin, the antimetabolite methotrexate and the immunosuppressant drug cyclosporine. Newer biologic agents that target specific steps in the immune system can also help control severe psoriasis. All these systemic therapies can have serious side effects and require an experienced physician to oversee their use. Still, systemic therapies offer new hope to patients who are disfigured and disabled by severe psoriasis. They demonstrate how modern science has made progress against a disease that has plagued man for thousands of years.
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A Man-ageable Malady
Most men pay much less attention to their skin than women. But when it comes to psoriasis, it would be a mistake to neglect itchy red scaly patches. Even though psoriasis is not curable, simple treatments can usually control early forms of the disease. More powerful drugs can help most men with advanced psoriasis.
Because psoriasis is linked to heart disease, men who are diagnosed with this common skin disorder should take extra steps to prevent heart problems. That means avoiding tobacco in all its forms, eating well, maintaining a health weight and taking extra steps (or getting other forms of exercise). And who knows? You might help fight psoriasis as you protect your heart.
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Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.