Psoriasis Linked To Seven New Genetic Variations

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Main Category: Eczema / Psoriasis
Also Included In: Immune System / Vaccines;  Arthritis / Rheumatology;  Genetics
Article Date: 03 Apr 2008 - 17:00 PDT

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Seven new sites of common DNA variation have been discovered that increase the risk of psoriasis. Some of these variations, in one area of the genome, link psoriasis and psoriatic arthritis to other autoimmune disorders. This work was published on April 4, 2008 in the open-access journal PLoS Genetics.

Psoriasis is an autoimmune disease characterized by a mistaken immune attack to the skin. It is identified by red, scaly patches on the skin that are itchy, painful, or both. It affects an estimated 7 million Americans. Additionally, 10-30% of patients with psoriasis develop psoriatic arthritis, a painful and debilitating arthritic condition additionally characterized by pitting or complete loss of fingernails.

There are many factors that may come into play in this condition, which make it difficult to study. This is true concerning its genetics as well. "Common diseases like psoriasis are incredibly complex at the genetic level," says lead investigator Anne Bowcock, Ph.D.. "Our research shows that small but common DNA differences are important in the development of psoriasis. Although each variation makes only a small contribution to the disease, patients usually have a number of different genetic variations that increases their risk of psoriasis and psoriatic arthritis."

The study, performed at the Washington University School of Medicine in St. Louis, was a comprehensive examination of the genetic basis of psoriasis. The researchers directed their attentions to points of common variation in the genome, known as single nucleotide polymorphisms (SNPs.) A large portion of the 3 billion nucleotides that make up the genome are identical from one person to the next, but some 10 million SNPs make someone unique. Of these, certain SNPs can influence disease and health in a person.

In a whole genome association study, the investigators scanned over 300,000 SNPs in the genomes of 223 psoriasis patients. This included 91 with psoriatic arthritis. The DNA of these patients was compared to that of 519 healthy patients in a control group, seeking specific differences between the groups. Then, a second study was performed with 577 psoriasis patients, 576 with psoriatic arthritis, and over 1,200 healthy controls.

The team discovered seven new variations that were linked to psoriasis. Additionally, the DNA variations that were located on chromosome 4 were strongly linked to psoriatic arthritis. These variations were also associated with type 1 diabetes, rheumatoid arthritis, Graves' disease (the result of an overproductive thyroid gland), and celiac disease (an inability to digest gluten).

These variations point scientists in the direction of different biological pathways that could underlie psoriasis on a basic level. This could eventually lead to new targeted drugs and treatments that attack specific pathways, according to Bowcock. She is now conducting a larger, genome-wide association study of psoriasis patients, and she expects to find additional genetic variations that are associated with the disease.

About PLoS Genetics

PLoS Genetics (http://www.plosgenetics.org) reflects the full breadth and interdisciplinary nature of genetics and genomics research by publishing outstanding original contributions in all areas of biology. All works published in PLoS Genetics are open access. Everything is immediately and freely available online throughout the world subject only to the condition that the original authorship and source are properly attributed. Copyright is retained by the authors. The Public Library of Science uses the Creative Commons Attribution License.

About the Public Library of Science

The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource. For more information, visit http://www.plos.org.

A Genome-Wide Association Study of Psoriasis and Psoriatic Arthritis Identifies New Disease Loci.
Liu Y, Helms C, Liao W, Zaba LC, Duan S, et al.
PLoS Genet 4(3): e1000041.
doi:10.1371/journal.pgen.1000041
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Written by Anna Sophia McKenney
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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