Skin Condition Vitiligo Tied to Immune System Dysfunction
WEDNESDAY April 21, 2010 -- Scientists have discovered several genes linked to vitiligo that confirm the skin condition is, indeed, an autoimmune disorder.
Vitiligo is a pigmentation disorder that causes white splotches to appear on the skin; the late pop star Michael Jackson suffered from the condition. The finding could lead to treatments for this confounding condition, the University of Colorado researchers said.
"If you can understand the pathway that leads to the destruction of the skin cell, then you can block that pathway," reasoned Dr. Doris Day, a dermatologist with Lenox Hill Hospital in New York City.
More surprisingly, however, was an incidental discovery related to the deadly skin cancer melanoma: People with vitiligo are less likely to develop melanoma and vice-versa.
"That was absolutely unexpected," said Dr. Richard A. Spritz, lead author of a paper appearing in the April 21 online issue of the New England Journal of Medicine.
This finding, too, could lead to better treatments for this insidious skin cancer.
Vitiligo, like a collection of about 80 other diseases including rheumatoid arthritis, type 1 diabetes and lupus, was strongly suspected to be an autoimmune disorder in which the body's own immune system attacks itself, in this case, the skin's melanocytes, or pigment-producing cells.
People with the disorder, which typically appears around the age of 20 or 25, develop white patches on their skin. Vitiligo it is fairly common, affecting up to 2 percent of the population.
But the question of whether or not vitiligo really is an autoimmune disease has been a controversial one, said Spritz, a professor in the Human Medical Genetics Program at the University of Colorado School of Medicine in Aurora.
At the urging of various patient groups, these authors conducted a genome-wide association study of more than 5,000 individuals, both with and without vitiligo.
Several genes found to be linked with vitiligo also had associations with other autoimmune disorders, such as type 1 diabetes and rheumatoid arthritis.
"We found genes that prove for sure that vitiligo is an autoimmune disease because these genes involve the immune system and some are seen in other autoimmune diseases like type 1 diabetes," Spritz said.
Then there was the surprise melanoma finding.
"We had wondered about this for many years. Could having an immune system that was revved up against pigment cells protect you against melanoma? And it turns out genetically to be the case," Spritz said. "The genetics that push you toward vitiligo push you away from melanoma and vice versa."
"We think that the immune system scavenges to protect us against melanoma and if it's hyper revved up, you're less likely to get melanoma and if it's down-regulated, you're more likely to get vitiligo," Spritz explained.
At this early stage of the game, this is clearly a double-edged sword for people who suffer from vitiligo.
And people with this condition are feeling a little left out in the cold, given that the discovery is most likely to benefit melanoma sufferers first, Spritz said.
In the not-too-distant future, genetic tests might be able to identify which melanoma patients would most be helped by immunotherapy.
But there's also hope also for vitiligo.
"We're starting to see the players directing the immune response," said Prashiela Manga, an assistant professor of dermatology at New York University Langone Medical Center in New York City. "We need to know what the genes are so we can develop treatments."
Visit the American Academy of Dermatology for more on vitiligo.
Posted: April 2010