Largest psoriasis meta-analysis to date yields new genetic clues

May 24, 2017
Credit: CC0 Public Domain

It's one of the most common immune-mediated diseases in the U.S., causing red, patchy and scaly marks on the skin. Yet the 1 to 2 percent of the population who have psoriasis are still left to wonder why.

A new study builds on the genetic architecture of , the next step toward answering what in the causes the disease. University of Michigan researchers, working with partners across the globe, published the work in Nature Communications. It's the most recent publication in long-standing psoriasis work at U-M.

"We know there are a lot of genes, each with a relatively small effect, in play. Those genes combined with the environment lead people to develop psoriasis," says senior author James T. Elder, M.D., Ph.D., professor of dermatology at the U-M Medical School. "This study identified 16 more genetic markers, bringing the total to 63 loci linked to psoriasis."

Elder's team ran genome-wide tests, comparing frequencies of genetic variants of people with psoriasis to those of control subjects. They examined data from eight different cohorts, with a total effective sample size of more than 39,000.

"This is by far the largest psoriasis meta-analysis to date in terms of sample size," says first author Alex Tsoi, Ph.D., a research assistant professor in dermatology, biostatistics and computational medicine and bioinformatics at the U-M Medical School. "We've been able to pinpoint pathways related to the disease as well as pointing to the right directions for the gene targets."

Zooming in

Elder's team focused in on the loci they have identified, to learn more about them.

Two pathways of note that are very important to the study of psoriasis include the IL-23 and HLA genes, Elder says. Many current therapies target IL-23 as well as IL-17, a cytokine that is produced in response to IL-23.

HLA "is by far the biggest genetic signal of psoriasis," Elder says. "We see through the nerve center of the immune system that the structure is more complicated than ever suspected." In fact, that region of genes includes seven different signals of psoriasis.

But even the largest psoriasis study so far doesn't turn up the data required to determine every genetic variant at play.

"We still haven't found more than half of what's genetic about psoriasis," Elder says. "Some of the differences are so subtle that we'd need to study hundreds of thousands of subjects."

Many samples, one population

The new study focused on subjects of European origin. Thanks to great partnerships across the globe, Elder says, other studies are investigating additional populations with psoriasis, including in India and China.

"Researchers are focusing on individual populations for each study, in order to understand the particulars of that population's genetic backgrounds," he says.

The work includes data from specialist-diagnosed psoriasis as well as self-reported, via the consumer genetics company 23andMe, one of the study collaborators. Researchers discovered some consumers might assume they have psoriasis without getting a formal diagnosis.

"There was some misclassification when the diagnosis was not from a dermatologist, and we estimated close to 4 percent of unaffected individuals thought they had psoriasis but they must have had something else," Tsoi says.

Once researchers adjusted for the false positives using a statistical approach, the self-reported cohort helped to not only identify the 16 new loci, but also confirm the others previously found.

"Adding that chunk of data really gave us power to see more signals than we had seen in the past," Elder says.

Working toward improved treatments

Although medications for psoriasis have come a long way over the years, Elder says only about 5 percent of the genes found so far are targeted by existing medications. Another issue in psoriasis treatment is high price tags for drugs, he adds.

"Better treatments will come out of understanding these other untouched genes," Elder says.

Explore further: Psoriasis may up risk of melanoma, hematologic cancer

More information: Nature Communications (2017). DOI: 10.1038/ncomms15382

Related Stories

Psoriasis may up risk of melanoma, hematologic cancer

March 28, 2017
(HealthDay)—Patients with psoriasis may have a higher risk of melanoma and hematologic cancers than the general population, according to a study published in the April issue of the Journal of the American Academy of Dermatology.

Severe psoriasis predominantly affects men

March 24, 2017
The fact that men are overrepresented in psoriasis registers and consume more psoriasis care have long led researchers to believe that the common skin disease disproportionally affects men. A unique study with 5,438 Swedish ...

Psoriasis impacts QoL for parents of affected children

January 23, 2017
(HealthDay)—Childhood psoriasis impacts parents' quality of life in multiple domains, especially their emotional well-being, according to a study published in the February issue of the Journal of the American Academy of ...

Psoriasis associated with diabetes, BMI and obesity in Danish twin study

April 27, 2016
The chronic inflammatory skin disease psoriasis was associated with type 2 diabetes, body mass index and obesity in a study of Danish twins, and the study also suggests the possibility of a common genetic cause between psoriasis ...

Recommended for you

Ecosystem approach makes urinary tract infection more treatable

September 22, 2017
The biological term 'ecosystem' is not usually associated with urinary tract infections, but this should change according to Wageningen scientists.

Investigators may unlock mystery of how staph cells dodge the body's immune system

September 21, 2017
For years, medical investigators have tried and failed to develop vaccines for a type of staph bacteria associated with the deadly superbug MRSA. But a new study by Cedars-Sinai investigators shows how staph cells evade the ...

Superbug's spread to Vietnam threatens malaria control

September 21, 2017
A highly drug resistant malaria 'superbug' from western Cambodia is now present in southern Vietnam, leading to alarming failure rates for dihydroartemisinin (DHA)-piperaquine—Vietnam's national first-line malaria treatment, ...

Individualized diets for irritable bowel syndrome better than placebo

September 21, 2017
Patients with irritable bowel syndrome who follow individualized diets based on food sensitivity testing experience fewer symptoms, say Yale researchers. Their study is among the first to provide scientific evidence for this ...

A dose of 'wait-and-see' reduces unnecessary antibiotic use

September 21, 2017
Asking patients to take a 'wait-and-see' approach before having their antibiotic prescriptions filled significantly reduces unnecessary use, a University of Queensland study has shown.

Groundbreaking investigative effort identifies gonorrhea vaccine candidates

September 19, 2017
Researchers at Oregon State University have identified a pair of proteins that show promise as the basis for a gonorrhea vaccine.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.