Bringing Psoriasis Under Control

Harvard Health Letters

Psoriasis is a chronic skin condition characterized by thick, raised red patches that are often covered with flaking, silvery scales. Although rarely life-threatening, it can dramatically affect a person's life. In his essay "At War with My Skin," the novelist John Updike, who developed psoriasis as a child, attributed his career choice to the isolating effects of the disease.

"Because of my skin," he wrote, "I counted myself out of any of those jobs...that demand being presentable. What did that leave? Becoming a craftsman of some kind, closeted and unseen -- perhaps a cartoonist or a writer, a worker in ink who can hide himself and send out a surrogate presence..."

Psoriasis can develop at any age and occurs in all races, but it's most likely to affect Caucasians and appear in early adulthood or at midlife. In the United States, seven to eight million people have some form of psoriasis. Although the condition affects both sexes equally, research suggests that it can cause more distress and embarrassment for women than for men.

Psoriasis is a lifelong condition, although it may go in and out of remission. It can be mild, moderate, or severe, depending on how extensively it affects a person's body and quality of life.

The goal of treatment is to reduce the frequency, length, and severity of outbreaks. \

In recent years, more effective therapies with fewer side effects have been developed; many of these new treatments target the immune system.

WHAT CAUSES PSORIASIS?

In psoriasis, certain immune system cells become overactive and cause the proliferation of skin cells called keratinocytes. Keratinocytes grow in the lower layers of the skin and slowly rise to the surface, a process called turnover that in most people takes about a month but in those with psoriasis takes only a few days. When their turnover is sped up in this way, the keratinocytes rise too quickly and pile up on the surface of the skin, producing thick, scaly red patches, called psoriatic plaques. These patches are red because small blood vessels grow to supply blood and nutrients to the area; these vessels also leak, allowing more immune cells to migrate into the already inflamed skin.

Psoriasis occurs when skin cells called keratinocytes turn over too rapidly. They form in the lower portion of the epidermis, the outer layer of skin. Normally, it takes about 28 days for these cells to move from the basal (lower) epidermis to the stratum corneum (upper layer). In a person with psoriasis, the process takes only three to four days. The cells quickly pile up and form raised red patches covered with flaking, silvery scales.

The underlying cause of this immune system malfunction is unknown, but the evidence suggests a complex interaction between genetic predisposition (about 40 percent of people with psoriasis have a family history of the disease) and environmental and lifestyle influences, including obesity, smoking, and heavy drinking. According to one theory, the culprit is an overreaction by the immune system to a triggering incident -- for example, stress, an infection (such as strep throat), a skin injury, or a medication (beta blockers or lithium, for example).

Another theory sees psoriasis as an autoimmune condition involving tumor necrosis factor-alpha (TNF-alpha), a substance involved in the body's normal response to infection. It's overproduced in people with psoriasis and may be provoking an immune system attack on their own tissues.

LINKS WITH OTHER CONDITIONS

There's increasing evidence that psoriasis, especially severe psoriasis, is associated with several other serious medical conditions. Two 2009 studies suggest that people with psoriasis have a higher rate of atherosclerosis, peripheral artery disease, heart attacks, strokes, and death from cardiovascular disease.

Psoriasis doesn't cause any of these diseases, but they share a couple of features, namely the presence of inflammation and the activity of certain proteins, called cytokines. Inflammation and cytokines are responsible for many of the symptoms of psoriasis and are also involved in the development of artery-clogging atherosclerosis and insulin resistance as well as possibly loss of bone density.

Whether treating psoriasis could reduce your risk of heart disease is unclear. But if you have psoriasis, you should pay especially close attention to cardiovascular risk factors, including blood pressure, cholesterol levels, smoking, exercise, and diet.

DIAGNOSIS AND TREATMENT

There are no laboratory tests for psoriasis, but most clinicians can diagnose plaque psoriasis, the most common form of the disease, from a physical examination and the patient's symptoms, medical history, and family history of the disease. Besides the characteristic plaques, symptoms can include pitted, discolored, and crumbly fingernails. Some people develop psoriatic arthritis, with joint pain, stiffness, and swelling, especially in the fingers.

The less common forms of psoriasis can be difficult for a general practitioner to recognize. For example, inverse psoriasis, which doesn't produce scaly skin, may be mistaken for a bacterial or fungal infection. A dermatologist can speed the diagnosis. (People with severe psoriasis should be followed by a dermatologist.) In rare cases, a skin biopsy may help rule out other disorders.

TYPES OF PSORIASIS

Plaque:

Slow-growing, thick, red lesions with silvery scales. Often develops on the scalp, elbows, knees, and back. May itch. About 85 percent to 90 percent of those who have psoriasis have this type of disease.

Inverse:

Large, smooth red areas without scales that develop in skin folds near the genitals, between the buttocks, under the breasts, or in the armpits.

Guttate:

Erupts quickly. Forms small, drop-like lesions (papules) that may become scaly. Most often appears on the trunk and limbs. Linked to strep throat.

Pustular:

Develops quickly, often with a fever, and can be severe. Small, red, pus-filled elevations (pustules) develop, sometimes clustering in sheets. Can form on the trunk, limbs, soles of the feet, and palms of the hands.

Erythrodermic:

Rare, life-threatening condition that causes redness and scaling all over the body. High risk of infection. Fluids and nutrients may be lost through the skin.

Currently, there's no cure for psoriasis, but many treatments can help reduce the symptoms and improve the appearance of the skin. Therapy depends on the type of psoriasis, the severity of the disease, and personal preferences.

The three main strategies, sometimes used in combination, are topical medications, ultraviolet light, and systemic treatments:

1. Topical medications.

For mild to moderate psoriasis, ointments, gels, creams, shampoos, and lotions are the usual first choice of treatment. They minimize scaling, tenderness, and itching by keeping the skin soft and well hydrated. The choice depends on convenience and the part of the body affected; for example, you may want to apply an ointment at night but use a cream during the day, because it's less greasy. Psoriasis doesn't necessarily get worse, so if you have mild psoriasis (one plaque on the knee and one on the elbow, for example), you may find that applying a moisturizer after bathing is all you need.

Coal tar is a time-honored treatment for psoriasis. It's not clear how it works but it seems to reduce the production of skin cells that form the scaly plaques. Coal tar products such as creams and shampoos are available without a prescription, but they can stain skin, hair, and clothes, so many people choose other, less messy topical preparations.

Corticosteroid creams act quickly to reduce inflammation and control itching, while also helping to prevent the formation of new lesions. They're typically applied twice a day until the skin clears or its appearance improves, and then intermittently to maintain the improvement. Long-term use of strong corticosteroids can cause skin damage, so you should use the least potent formulation that controls your symptoms.

Newer topical therapies that have proved effective include two forms of vitamin D -- calcipotriene (Dovonex) and calcitriol (Vectical) -- available only by prescription. They are equally effective, but calcitriol appears to cause less skin irritation. Both drugs are thought to inhibit the proliferation of keratinocytes. Another topical therapy is tazarotene (Tazorac), a retinoid -- a synthetic form of vitamin A. It can dry the skin, so you may need to use a moisturizer along with it.

2. Ultraviolet (UV) light.

Psoriasis often improves in the summer, because the skin is exposed more to the ultraviolet radiation in sunlight, which kills rapidly proliferating cells. But there's no need to wait until June. Controlled exposure to ultraviolet B (UVB) radiation, called phototherapy, can be used any time of the year, alone or in combination with topical agents. Treatment usually requires 30 sessions (three sessions per week for 10 weeks) at a hospital or clinic; home phototherapy systems are also available.

Phototherapy has a cousin called photochemotherapy, in which the patient is exposed to ultraviolet A (UVA) radiation after taking a photosensitizing drug. UVA penetrates deeper than UVB and is less likely to burn the skin, but it raises the risk of skin cancer, so if you choose this treatment, you'll need to have a dermatologist check your skin regularly. In still another type of UV light treatment, a high-energy laser is focused directly on the psoriasis lesions. Because the rest of the skin is not affected, higher doses of UVB can be used. Insurance coverage for UV light therapy is spotty, so check with your insurance carrier before starting treatment.

3. Systemic treatments.

More severe psoriasis may require treatment with drugs taken orally or by injection that work systemically (throughout the body). Anyone using a systemic therapy should be closely monitored by an experienced clinician, because all of the drugs can produce serious side effects. The tests needed to monitor these side effects are expensive, and so are most of the agents themselves. We don't always have information on their long-term safety and effectiveness, either. Still, they can dramatically improve the quality of life for people who have severe, disabling, or disfiguring psoriasis.

There are two types of systemic therapies used for the treatment of psoriasis: traditional systemics and "biologics."

Traditional systemics.

These include methotrexate, cyclosporine, and acetretin (Soriatane). Methotrexate is the most commonly prescribed systemic therapy. Originally used to treat cancer, it works by inhibiting an enzyme involved in the rapid growth of cells. (The doses given for psoriasis and psoriatic arthritis are much lower than those used in cancer chemotherapy.) Oral cyclosporine works by stopping the activity of certain immune cells and slowing the growth of skin cells.

The risks of methotrexate include liver and kidney damage; the risks of cyclosporine, kidney damage and high blood pressure. Acetretin (Soriatane) is a retinoid, which is thought to work by helping to control the multiplication of cells. It's often recommended for the pustular and erythrodermic forms of psoriasis. Possible side effects include lip inflammation and hair loss.

Women who are or could become pregnant should not take methotrexate, cyclosporine, or acetretin, and women who take acetretin should avoid becoming pregnant for three years after stopping the drug.

Biologics.

These are immunomodulatory drugs, which work by inhibiting the effects of several immune system components, including TNF-alpha, IL-12, and IL-23. These drugs are important treatment alternatives for people with moderate to severe plaque psoriasis and those who haven't responded to other therapies. Biologic treatments include adalimumab (Humira), etanercept (Enbrel), infliximab (Remicade), ustekinumab (Stelara), and alefacept (Amevive). -- Harvard Women's Health Watch

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