Several genetic risk loci unique to psoriatic arthritis have been identified in a study of samples from 1,962 patients with the disease and 8,923 healthy population controls of white ancestry, according to Dr. John Bowes and his associates.

The investigators used Immunochip genotyping array to fine map previously reported immune-related susceptibility loci, including known psoriasis susceptibility loci, to identify novel psoriatic arthritis (PsA) susceptibility loci.

They found a risk locus specific to PsA at chromosome 5q31, and they detected PsA risk variants at chromosome 1q31, a known psoriasis susceptibility locus. They found independent associations between PsA and three human leukocyte antigen (HLA) genes as well as three non-HLA loci. Finally, they determined that the PsA genetic risk variants preferentially associated with epigenetic markers of open chromatin in CD8+ memory primary T cells, supporting “their importance in the underlying disease mechanism.”

Until this point, the majority of risk loci associated with PsA were shared with psoriasis, but the discovery of unique risk loci could begin to explain fundamental differences between psoriasis and PsA, the investigators said.

Read the full study published Feb. 5 in Nature Communications (doi:10.1038/ncomms7046).