Psoriasis Linked To Seven New Genetic Variations

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.



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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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Here For Full Length Article



Written by Anna Sophia McKenney