Using the data from the Nature Genetics study, Feng, Goldgar, and colleagues employed two statistical methods, imputation and logistic regression analysis, to determine with a much greater degree of accuracy those genes that have the highest association with psoriasis. Using imputation they were able to reliably predict the *0602 status of all subjects in the recent Nature Genetics study. This did two things; first, it increased the confidence that *0602 is the major genetic variation on this chromosome and, second, it permitted them to determine if there was any other associated genetic variation in this region.

Removing the strong effect of *0602 resulted in the identification of two other loci (fixed position on a chromosome) that are independently associated with psoriasis (MICA/HLA-B and c6orf10). These two loci increased the risk for the disease by 1.23 and 1.6 times, respectively. However, when all three genetic variations that Feng, Goldgar, and colleagues report are present, the risk for psoriasis is 8.9 times higher than when none of these is present.

To confirm the results, the researchers examined an independent patient population in China, which corroborated their conclusions.

While *0602 and the associated, but independent, genetic variations reported have a major genetic contribution to psoriasis, many other genes undoubtedly play a role, according to Krueger. The number of DNA sites discovered to have strong associations with psoriasis has more than doubled in the past two years.

Source: University of Utah Health Sciences