Named for the Greek word psra meaning "itch," psoriasis is a chronic,non-contagious disease characterized by inflamed lesions covered with silvery-white scabs of dead skin.

Psoriasis, which affects at least four million Americans, is slightly more common in women than in men. Although the disease can develop at any time, and10-15% of all cases are diagnosed in children under 10, and the average age at the onset of symptoms is 28. Psoriasis is most common in fair-skinned people and extremely rare in dark-skinned individuals.

Normal skin cells mature and replace dead skin every 28-30 days. Psoriasis causes skin cells to mature in less than a week. Because the body can't shed old skin as rapidly as new cells are rising to the surface, raised patches of dead skin develop on the arms, back, chest, elbows, legs, nails, folds betweenthe buttocks, and scalp.

Psoriasis is considered mild if it affects less than 5% of the surface of thebody; moderate, if 5-30% of the skin is involved, and severe, if the diseaseaffects more than 30% of the body surface.

Dermatologists distinguish different forms of psoriasis according to what part of the body is affected, how severe symptoms are, how long they last, and the pattern formed by the scales.

Plaque psoriasis (psoriasis vulgaris), the most common form of the disease, is characterized by small, red bumps that enlarge, become inflamed, and form scales. The top scales flake off easily and often, but those beneath the surface of the skin clump together. Removing these scales exposes tender skin, which bleeds and causes the plaques (inflamed patches) to grow.

Plaque psoriasis can develop on any part of the body, but most often occurs on the elbows, knees, scalp, and trunk.

At least 50 of every 100 people who have any form of psoriasis have scalp psoriasis. This form of the disease is characterized by scale-capped plaques onthe surface of the skull.

The first sign of nail psoriasis is usually pitting of the fingernails or toenails. Size, shape, and depth of the marks vary, and affected nails may thicken, yellow, or crumble. The skin around an affected nail is sometimes inflamed, and the nail may peel away from the nail bed.

Named for the Latin word gutta, which means "a drop," guttate psoriasis is characterized by small, red, drop-like dots that enlarge rapidly and maybe somewhat scaly. Often found on the arms, legs, and trunk and sometimes inthe scalp, guttate psoriasis can clear up without treatment or disappear andresurface in the form of plaque psoriasis.

Pustular psoriasis usually occurs in adults. It is characterized by blister-like lesions filled with non-infectious pus and surrounded by reddened skin. Pustular psoriasis, which can be limited to one part of the body (localized) or can be widespread, may be the first symptom of psoriasis or develop in a patient with chronic plaque psoriasis.

Generalized pustular psoriasis is also known as Von Zumbusch pustular psoriasis. Widespread, acutely painful patches of inflamed skin develop suddenly. Pustules appear within a few hours, then dry and peel within two days.

Generalized pustular psoriasis can make life-threatening demands on the heartand kidneys.

Palomar-plantar pustulosis (PPP) generally appears between the ages of 20 and60. PPP causes large pustules to form at the base of the thumb or on the sides of the heel. In time, the pustules turn brown and peel. The disease usually becomes much less active for a while after peeling.

Acrodermatitis continua of Hallopeau is a form of PPP characterized by painful, often disabling, lesions on the fingertips or the tips of the toes. The nails may become deformed, and the disease can damage bone in the affected area.

Inverse psoriasis occurs in the armpits and groin, under the breasts, and inother areas where skin flexes or folds. This disease is characterized by smooth, inflamed lesions and can be debilitating.

Characterized by severe scaling, itching, and pain that affects most of the body, erythrodermic psoriasis disrupts the body's chemical balance and can cause severe illness. This particularly inflammatory form of psoriasis can be the first sign of the disease, but often develops in patients with a history ofplaque psoriasis.

About 10% of partients with psoriasis develop a complication called psoriaticarthritis. This type of arthritis can be slow to develop and mild, or it candevelop rapidly. Symptoms of psoriatic arthritis include:

  • Joint discomfort, swelling, stiffness, or throbbing
  • Swelling in the toes and ankles
  • Pain in the digits, lower back, wrists, knees, and ankles
  • Eye inflammation or pink eye (conjunctivitis)

The cause of psoriasis is unknown, but research suggests that an immune-system malfunction triggers the disease. Factors that increase the risk of developing psoriasis include:

  • Family history
  • Stress
  • Exposure to cold temperatures
  • Injury, illness, or infection
  • Steroids and other medications
  • Race

Trauma and certain bacteria may trigger psoriatic arthritis in patients withpsoriasis.

A complete medical history and examination of the skin, nails, and scalp arethe basis for a diagnosis of psoriasis. In some cases, a microscopic examination of skin cells is also performed.

Blood tests can distinguish psoriatic arthritis from other types of arthritis. Rheumatoid arthritis, in particular, is diagnosed by the presence of a particular antibody present in the blood. That antibody is not present in the blood of patients with psoriatic arthritis.

Age, general health, lifestyle, and the severity and location of symptoms influence the type of treatment used to reduce inflammation and decrease the rate at which new skin cells are produced. Because the course of this disease varies with each individual, doctors must experiment with or combine differenttreatments to find the most effective therapy for a particular patient.

Steroid creams and ointments are commonly used to treat mild or moderate psoriasis, and steroids are sometimes injected into the skin of patients with a limited number of lesions. In mid-1997, the United States Food and Drug Administration (FDA) approved the use of tazarotene (Tazorac) to treat mild-to-moderate plaque psoriasis. This water-based gel has chemical properties similar to Vitamin A.

Brief daily doses of natural sunlight can significantly relieve symptoms. Sunburn has the opposite effect.

Moisturizers and bath oils can loosen scales, soften skin, and may eliminatethe itch. So can adding a cup of oatmeal to a tub of bath water. Salicylic acid (an ingredient in aspirin) can be used to remove dead skin or increase theeffectiveness of other therapies.

Administered under medical supervision, ultraviolet light B (UVB) is used tocontrol psoriasis that covers many areas of the body or that has not responded to topical preparations. Doctors combine UVB treatments with topical medications to treat some patients and sometimes prescribe home phototherapy, in which the patient administers his own UVB treatments.

Photochemotherapy (PUVA) is a medically supervised procedure that combines medication with exposure to ultraviolet light (UVA) to treat localized or widespread psoriasis. An individual with wide-spread psoriasis that has not responded to treatment may enroll in one of the day treatment programs conducted atspecial facilities throughout the United States. Psoriasis patients who participate in these intensive sessions are exposed to UVB and given other treatments for six to eight hours a day for two to four weeks.

Methotrexate (MTX) can be given as a pill or as an injection to alleviate symptoms of severe psoriasis or psoriatic arthritis. Patients who take MTX mustbe carefully monitored to prevent liver damage.

Psoriatic arthritis can also be treated with nonsteroidal anti-inflammatory drugs (NSAIDS), like acetaminophen (Tylenol) or aspirin. Hot compressesand warm water soaks may also provide some relief for painful joints.

Other medications used to treat severe psoriasis include etrentinate (Tegison) and isotretinoin (Accutane), whose chemical properties are similar to thoseof Vitamin A. Most effective in treating pustular or erythrodermic psoriasis, Tegison also relieves some symptoms of plaque psoriasis. Tegison can enhance the effectiveness of UVB or PUVA treatments and reduce the amount of exposure necessary.

Accutane is a less effective psoriasis treatment than Tegison, but can causemany of the same side effects, including nosebleeds, inflammation of the eyesand lips, bone spurs, hair loss, and birth defects. Tegison is stored in thebody for an unknown length of time, and should not be taken by a woman who is pregnant or planning to become pregnant. A woman should use reliable birthcontrol while taking Accutane and for at least one month before and after hercourse of treatment.

Cyclosporin emulsion (Neoral) is used to treat stubborn cases of severe psoriasis. Cyclosporin is also used to prevent rejection of transplanted organs, and Neoral, approved by the FDA in 1997, should be particularly beneficial topsoriasis patients who are young children or African-Americans, or those whohave diabetes.

Other conventional treatments for psoriasis include:

  • Capsaicin (Capsicum frutecens), an ointment that can stop production of the chemical that causes the skin to become inflamed and halts the runaway production of newskin cells. Capsaicin is available without a prescription, but should be used under a doctor's supervision to prevent burns and skin damage.
  • Hydrocortisone creams, topical ointments containing a form of vitamin D called calcitriol, and coal-tar shampoos and ointments can relieve symptoms but may cause such side effects as folliculitis (inflammation of hair follicles) and heightened risk of skin cancer.

Most cases of psoriasis can be controlled, and most people who have psoriasiscan live normal lives.

Some people who have psoriasis are so self-conscious and embarrassed about their appearance that they become depressed and withdrawn. The Social SecurityAdministration grants disability benefits to about 400 psoriasis patients each year, and a comparable number die from complications of the disease.

A doctor should be notified if:

  • Psoriasis symptoms appear or reappearafter treatment
  • Pustules erupt on the skin and the patient experiences fatigue, muscle aches, and fever
  • Unfamiliar, unexplained symptomsappear.

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