Twenty-three new genes involved in risk for autoimmune vitiligo have been identified by an international group of scientists led by the University of Colorado School of Medicine.
Vitiligo is a chronic condition in which melanocytes — the cells that make pigment — in the skin are destroyed.
As a result, white patches appear on the skin in different parts of the body. Similar patches also appear on both the mucous membranes, and perhaps in the retina. The hair that grows on areas affected by vitiligo sometimes turns white.
The cause of vitiligo is not known, but scientists have several different theories.
There is strong evidence that people with vitiligo inherit genes that make them susceptible to depigmentation.
The most widely accepted view is that the depigmentation occurs because vitiligo is an autoimmune disease — a disease in which a person’s immune system reacts against the body’s own organs or tissues.
People’s bodies produce proteins called cytokines that, in vitiligo, alter their pigment-producing cells and cause these cells to die. Another theory is that melanocytes destroy themselves.
Some patients have reported that a single event, such as sunburn or emotional distress, triggered vitiligo. However, these events have not been scientifically proven as causes of vitiligo.
A better understanding of the causes of vitiligo could also lead to breakthroughs in several other autoimmune diseases, including autoimmune thyroid disease, pernicious anemia, rheumatoid arthritis, adult-onset type 1 diabetes, Addison’s disease, and lupus.
“Our study doubles the number of known genes involved in risk for vitiligo,” said senior author Prof. Richard Spritz, Director of the Human Medical Genetics and Genomics Program at the University of Colorado School of Medicine.
Prof. Spritz and co-authors conducted genome-wide association studies on 4,680 people with vitiligo and 39,586 control cases and found the genes that provide a framework for the genetic architecture and biological mechanisms of vitiligo and highlight relationships with other autoimmune diseases and melanoma.
The team is trying to identify causal mutations in these genes by using DNA sequencing and genetic studies involving a large number of vitiligo patients from various different ethnic groups. This study focused on subjects of European ancestry.
“One of the purposes of the genome project was to give us the tools to do more complicated disease analysis,” Prof. Spritz explained.
“What’s emerging in general for complex diseases is that it is changes in gene regulation rather than gene structure that are causes.”
The researchers also found associations between genes indicated in some of other autoimmune diseases and vitiligo, and while it remains uncertain whether they reflect shared or different causes, it offers promising areas for future research.
The team’s results were published online October 10 in the journal Nature Genetics.
Ying Jin et al. Genome-wide association studies of autoimmune vitiligo identify 23 new risk loci and highlight key pathways and regulatory variants. Nature Genetics, published online October 10, 2016; doi: 10.1038/ng.3680