Psoriasis just masquerades as skin disease
Actually an autoimmune disorder, it carries consequences for the whole body

By Dennis Thompson
HealthDay Reporter

(HealthDay News) -- A common test of inductive reasoning goes like this: If it looks like a duck, swims like a duck and quacks like a duck, then it's probably a duck. But the disease psoriasis defies that logic.

A frustrating, maddening and painful disease, psoriasis causes thick, scaly lesions to form on all parts of a person's body. The scales itch and ache and drive people to distraction.

But psoriasis is not really a skin disease.

"For many years, psoriasis has been considered a skin disease when it's really an autoimmune disease that affects the skin," said Bruce Bebo, director of research and medical programs for the National Psoriasis Foundation.

Doctors are just beginning to better understand the implications of psoriasis as an autoimmune disease. That knowledge is helping them figure out how the inflammation caused by psoriasis is tied to other chronic conditions. And they are pursuing new and better cures because of the improved understanding of psoriasis.

"I think we've made more headway in the last 15 years than the last 100 years preceding, but our understanding of psoriasis is still very childlike," said Dr. Lawrence J. Green, a dermatologist in Rockville , Md. , and a member of the National Psoriasis Foundation's board of trustees.

As many as 7.5 million Americans, about 2.2 percent of the population, has psoriasis, according to the U.S. National Institutes of Health. August has been designated Psoriasis Awareness Month.

No cure exists for psoriasis, although there are treatments that can soothe and heal the lesions caused by the disease. It's not contagious, but it does appear to run in families. About one of every three people with psoriasis report having a relative with the disease, according to the National Psoriasis Foundation. A child of parents who both have psoriasis has a 50-50 chance of developing it.

From 10 to 30 percent of people with psoriasis also develop psoriatic arthritis, a chronic inflammation of the joints that can cause permanent joint degeneration if left untreated.

Psoriasis also is linked to other diseases, though experts are still figuring out how the autoimmune response that prompts it affects other parts of the body.

A study released in April strengthened the suspicion held by many that psoriasis is linked to diabetes and hypertension. The research found that women with psoriasis had a 63 percent increased risk of developing diabetes and a 17 percent increased risk of developing high blood pressure, compared with women who did not have psoriasis.

Bebo said the inflammation caused by psoriasis causes systemic damage. "There are consequences for the rest of the body due to this continual inflammatory state," he said.

People with psoriasis need to get the disease under control to avoid damage to their body. "The most important message from this study is to see your doctor for effective treatment," Green said. "You'll not only look better, you'll feel better."

Researchers also might be closing in on one of the mechanisms that causes psoriasis to develop, he said.

Psoriasis is believed to occur when a person's immune system mistakenly activates T cells, a type of white blood cell, according to the American Academy of Dermatology. The T cells cause inflammation that speeds up production of skin cells, resulting in the lesions. However, no one is certain what prompts the immune system to activate the T cells.

Another new study has shown that people with psoriasis tend to have excessive amounts of antimicrobial peptides on the surface of the skin. Doctors suspect that these peptides might couple with the DNA from dying skin cells to produce an autoimmune reaction that results in psoriasis.

"No one really knows what the trigger is for psoriasis," he said. "This recent study may show that DNA from dying cells could be that trigger."

The treatment of psoriasis suffered a setback, however, in April when the maker of a psoriasis medication called Raptiva (efalizumab) pulled the drug from the market. The move came about two months after U.S. health officials issued a public health advisory on the drug after confirming a link to a rare but sometimes fatal brain infection.

"Psoriasis is different in different people, and different people respond to different drugs," Bebo said. "It's disappointing that we have one less tool in the toolbox to fight this disease."

Bebo noted that Raptiva had proven helpful to about 2,000 people with psoriasis in the United States . "For some of those people, they're in a difficult place right now," he said.

On the other hand, a promising new biologic drug is awaiting approval by the U.S. Food and Drug Administration: Stelara (ustekinumab), which affects immune mediators not targeted by any other psoriasis drug. It holds great promise for helping people who don't respond to other medications, Bebo said.

"It's really a brand new tool that's different from any other tool we have," he said, noting that Stelara has been approved for use in Canada and Europe .

On the Web

To learn more about psoriasis, visit the U.S. National Library of Medicine.

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