University of Michigan study brings mysteries of psoriasis closer to being solved

Ann Arbor, Mich.-Researchers at the University of Michigan Medical School report they’ve isolated a common genetic variation in an immune-system gene that makes carriers significantly more susceptible to developing psoriasis.

The gene, named PSORS-1, is described as the first genetic determinant of psoriasis to be definitively identified in a major clinical study. The PSORS-1 gene is actually one of more than 20 different varieties, or alleles, of a gene known as HLA-C. The researchers say its identification could lead to new treatments that will have less risk and fewer side effects than current therapies.

According to lead author Rajan P. Nair, Ph.D., a University of Michigan assistant research professor in dermatology, scientists have been searching for genes associated with psoriasis for three decades, but until now research has been inconclusive. In a previous study, Nair and his colleagues had narrowed the search for the PSORS1 gene down to a 300,000-base-pair segment of chromosome 6 that included a gene called HLA-C and at least 10 other genes. Located on human chromosome 6, HLA-C is one of several genes in the major histocompatibility complex (MHC) that regulate how the immune system fights off infection.

“We started this study in 1991 expecting to find that psoriasis is a single-gene disease, and now we’ve found that it’s not,” Dr. Nair tells Dermatology Times. “In short, we looked at these 11 genes and found the HLA-C gene to be the most interesting in that it’s an immune gene and the most likely to be carried by people susceptible to psoriasis.”

While the study’s findings specify PSORS-1 as the major gene involved in susceptibility to psoriasis, it’s not the only one. According to Dr. Nair, further substantial research will be required to find the other genes involved in psoriasis and then to develop a more effective treatment to combat the disease. The key, says the study, is to find which branches of the immune system trigger psoriasis in certain people and find a way to neutralize them without affecting the entire immune system.

The University of Michigan study looked at 2,723 people from 678 families from which at least one family member had psoriasis. Results are to be published in the May issue of the American Journal of Human Genetics.