Vitiligo Confirmed Auto Immune, May Provide Skin Cancer Protection
Vitiligo is a skin pigmentation disorder first brought to a greater awareness when Michael Jackson revealed that he had the condition in 1986. This week, new research has confirmed that vitiligo is an autoimmune disease and shares an unexpected link to malignant melanoma.
Vitiligo is a disorder that affects one in 200 people, causing pale skin patches that lack pigment and burn easily. The condition occurs in all races and ethnicities, but it is more noticeable in those with darker skin. There is currently no cure although the condition can be managed through steroid creams and treatment with ultraviolet light.
Because damage from sunburn is a risk factor for skin cancer, the researchers were surprised to find that a common gene mutation that increases the chance of vitiligo actually cuts cancer risk.
Researchers examined the genes of 1514 patients of European white ancestry who had generalized vitiligo and compared them with 2813 others of similar descent who did not have the condition. Seven genes in total were linked to vitligo. The genes identified were already associated with auto-immune conditions such as type 1 diabetes, rheumatoid arthritis and lupus.
In particularly, the disease was associated with the major alleles of single nucleotide polymorphisms (SNP’s) in the TYR genetic locus. This gene encodes tyrosinase, the key enzyme in melanocytes, the pigment-producing cells that synthesize melanin. Melanin gives skin its color and protects against harmful UV rays from the sun.
"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," explained Richard Spritz MD of the University of Colorado in Aurora.
Study author Professor Dot Bennett, from St George's, University of London, still warned: "Although this may provide some consolation for people with vitiligo, they should still be careful in the sun. As they know, they sunburn quickly, and a lower risk of cancer doesn't mean zero."
The findings can lead to better treatments, or perhaps a cure, for vitligo and can lead to better treatment options for malignant melanoma patients, said Dr. Spritz. Genetic testing for tyrosinase and other genes in the study could determine the best candidates for melanoma-fighting immunotherapies, such as interleukin 2 and various vaccines.
The genetic association, however, only accounted for 7.4% of the total genetic risk for generalized vitiligo, and the variants do not exist outside of Caucasian people. The next step, already underway, is to examine the association in other racial and ethnic populations with the disease.
Jin Y, et al "Variant of TYR and autoimmunity susceptibility loci in generalized vitiligo" N Engl J Med 2010.