Vitiligo is more extensive in U.S.-born patients

By Rob Goodier

NEW YORK (Reuters Health) - Vitiligo appears to strike US patients harder than those born elsewhere, a new study suggests.

In vitiligo, patches of skin lose pigmentation and become lighter in color. Patients born outside of the U.S. were much less likely to have more than 25% of their skin area affected, with an age, gender and race-adjusted odds ratio of 0.57, the study found.

Because vitiligo is thought to be an autoimmune disorder, a possible explanation lies in the hygiene hypothesis, the researchers said in their report, but the study did not yield any conclusions.

"It's hard to draw clinical conclusions from an epidemiology study such as this. This work is hypothesis-generating in the sense that we have not previously recognized such regional differences," study leader Dr. Jonathan Silverberg, a dermatologist at Northwestern University in Chicago, told Reuters Health by email.

Dr. Silverberg and his team published their findings July 9 online in JAMA Dermatology.

"There are well established environmental factors that influence other skin disorders such as eczema. There are likely multiple environmental factors that are similarly contributing to our findings in vitiligo," Dr. Silverberg said.

The researchers gathered responses from nearly 2,800 vitiligo patients worldwide who filled out an online survey. Of those, 72% live in the United States.

The study found that simply being born outside of the U.S. lowered the odds of depigmentation of more than 25% of the skin - even if the patient had moved to live in the States.

That finding led the researchers to ask if there were regional differences within the U.S., and indeed, they found more severe afflictions in the southern states and northern Great Plains. The proportion of patients with at least 25% depigmentation ranged from 27% in Maryland to 100% in the midwest states of North Dakota, South Dakota and Wyoming.

Another factor that reduced the odds of greater body coverage appears to be the patient's distance from the equator. Those who are born and live closer to the equator are less likely to have more than 25% of their skin depigmented, the study found.

"We hope that this work will inspire future research to investigate the role of environmental factors in vitiligo," Dr. Silverberg said.

SOURCE: http://bit.ly/Wi1Uif

JAMA Dermatol 2014.

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