Researchers at Washington University School of Medicine in St. Louis have discovered seven new sites of common DNA variation that increase the risk of this skin condition. They also found that variations in one genetic region link psoriasis and psoriatic arthritis to other autoimmune disorders.

The researchers focused on points of common variation in the genome called single nucleotide polymorphisms, or SNPs. While most of the 3 billion nucleotides that comprise DNA are thought to be identical from one person to the next, some 10 million SNPs build variation into the genome and make each individual unique. Some of these SNPs play a crucial role in a person’s predisposition to disease or good health.

Using an approach known as whole genome association, the investigators scanned more than 300,000 SNPs in the genomes of 223 psoriasis patients, including 91 who had psoriatic arthritis. They compared the DNA variations in people with psoriasis to those found in 519 healthy control patients, looking for specific differences that may be linked to the disease. They then replicated their findings in a larger set of patients – 577 with psoriasis and 576 with psoriatic arthritis – and more than 1,200 healthy controls.

Anne Bowcock and her team found seven novel DNA variations linked to psoriasis. Notably, DNA variations on chromosome 4 were strongly linked to psoriatic arthritis. These same variations were also associated with psoriasis and had been previously linked to type 1 diabetes, rheumatoid arthritis, Grave’s disease, and celiac disease.

The variations identified by this research team point to different biological pathways that underlie psoriasis and may eventually lead to new targeted drugs and treatments that hit specific pathways, Bowcock says.

Source; PLoS Genetics, 2008

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