The results showed that people with blue eyes were less likely to develop vitiligo. Meanwhile, people with brown eyes were more likely to develop the skin disease and its characteristic white patches of skin and hair.
Researchers say the findings suggest eye color may also have important implications on melanoma risk because the two diseases are related genetically.
"Genetically, in some ways vitiligo and melanoma are polar opposites," researcher Richard Spritz, MD, director of the Human Medical Genetics and Genomics Program at the University of Colorado School of Medicine, says in a news release. "Some of the same genetic variations that make one more likely to have vitiligo make one less likely to have melanoma, and vice versa."
Vitiligo is an autoimmune disease in which a person's immune system attacks normal pigment cells, causing irregular white patches of skin and hair. People with vitiligo are also at higher risk of developing other autoimmune diseases like autoimmune thyroid disease, type 1 diabetes, rheumatoid arthritis, and lupus.
Melanoma is the most deadly form of skin cancer.
Eye Color Tied to Skin Risk
In the study, published in Nature Genetics, researchers looked at the genes associated with vitiligo in 450 people with the skin disease and at a comparison group of nearly 3,200 Americans of non-Hispanic European ancestry.
The analysis identified 13 new genes that predispose people to vitiligo.
The results also showed that a lower percentage of people with blue or gray eyes and a higher percentage of people with brown eyes had vitiligo than would be expected with the normal distribution of eye colors.
For example, among the people with vitiligo:
- 27% had blue or gray eyes, compared with 52% of Americans of European descent without the condition.
- 43% had tan or brown eyes vs. 27%.
- 30% had green or hazel eyes vs. 22%.
Researchers say the abnormal immune response associated with vitiligo may have effects in lowering the risk of melanoma.
"We think that vitiligo represents over-activity of a normal process by which one's immune system searches out and destroys early cancerous melanoma cells," says Spritz.
He says as researchers learn more about the genes associated with vitiligo, they may learn more about the genes involved in other autoimmune diseases as well as melanoma.