By Deborah Rafferty

Having a severe skin disease is a lot like Neapolitan ice cream8212;at least, according to U researchers.
Researchers at the U School of Medicine’s department of dermatology have identified three specific genetic variations that will increase the likelihood of a person developing psoriasis, a severe skin rash. The different combinations of these genetic variations could lead to different types and severities of psoriasis.
“Take these three findings and label them as flavors of ice cream, the question becomes what flavor you have,” said professor of dermatology Gerald Krueger about the different combinations of the types of genetic variation. “If you have none, what is the risk of developing psoriasis? What is the risk if you have all three?”
Researchers re-examined areas previously identified in the past to have a significant association with psoriasis so they could better determine if there were any other genetic variations that contributed to the development of the disease, said Kristina Callis Duffin, an assistant professor of dermatology.
A study published in the Aug. 13 issue of PLoS Genetics identified four new hotspots and confirmed two more. It also identified two genetic variations on a chromosome that have a major association with psoriasis. If a patient has all three genetic variations, then the risk of developing psoriasis increases to about 9 percent, said Krueger, who is also Benning Presidential endowed chair holder, and a co-author of the study.
Although these three genetic variations play an important role, many other genes undoubtedly contribute to the development of psoriasis. In a study earlier this year, researchers identified 18 other genes and genetic variations and seven main genetic hotspots that had the strongest association with psoriasis.
The new U study focused on how the disease affects a wider population, expanding the number of participants from about 1,400 to 5,000. Researchers examined both those with the disease and those unaffected by psoriasis, Krueger said.
A chronic skin disease that causes patients to develop red scaly patches, psoriasis affects around 7.5 million people in the United States, and about 25 percent of those will develop psoriatic arthritis. Researchers have confirmed that though genetics play a major role in the disease, if patients has psoriasis, it does not necessarily mean that it will be passed on to their children, Krueger said.
“It’s a very complex disease,” he said. “It’s not a simple inheriting issue. You can acquire genetic alterations.”
Researchers plan to continue studying the disease to better understand what exactly causes psoriasis. They will take a closer look at the molecular level and the areas around the hotspots to find more specifically what is involved in driving the disease expression, Krueger said. In addition, the researchers want to be able to determine how the different genetic variations are associated with the different types of psoriasis and will be part of a future study.
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