Rosacea is estimated to affect up to 16 million people in the United States alone, with symptoms typically including redness, visible blood vessels, and pimple-like sores on the skin of the central face.

Because rosacea affects facial appearance, it can also have a psychological impact on those who suffer from it, according to surveys by the National Rosacea Society.

A new paper studied the data of more than 46,000 23andMe customers and found two genetic variants strongly associated with the disease among people of European ancestry. 23andMe has controversially claimed in the past that they are not bound by normal informed consent rules because no one personally visits their office and they affirm that this work was done under a protocol approved by the AAHRPP-accredited institutional review board, Ethical and Independent Review Services.

The authors found that the genetic variants - single nucleotide polymorphisms (SNPs) - associated with rosacea are in or near the HLA-DRA and BTNL2 genes, which are associated with other diseases, including diabetes and celiac disease.

The genome-wide association study was broken into two parts: discovery and validation. First, data from 22,000 23andMe customers was examined. More than 2,600 customers reported having received a rosacea diagnosis from a physician. The remainder of the study participants did not have the condition and were treated as controls. To validate findings from this initial group, 23andMe researchers then tested the identified SNPs with a separate group of 29,000 consented 23andMe customers (3,000 rosacea patients, 26,000 controls). The researchers were able to confirm the same association with rosacea. 

"This is another example of how 23andMe can help in researching common yet poorly understood diseases," said Joyce Tung, Ph.D., 23andMe's director of research and a co-author of the paper. "The study also speaks to the power of large data sets in studying and identifying genetic associations."

In addition to the genome-wide association study, the research included obtaining skin biopsies from six individuals with rosacea and showed that both HLA-DRA and BTNL2 proteins can be found in the skin of people with rosacea. This preliminary work hints toward the biological relevance of HLA-DRA and BTNL2 in rosacea.

Published in the Journal of Investigative Dermatology.