IL-23A, IL-23R, IL-17A and IL-17R polymorphisms in different psoriatic arthritis clinical manifestations in the northern Italian population

To investigate the genetic variability of IL-17A, IL17-RA, IL-23A and IL-23R genes on an in-depth phenotypically characterized northern Italian Psoriatic arthritis (PsA) case-control cohort, in search for associations specific to different PsA clinical sub-phenotypes. We examined 118 patients with PsA according to CASPAR criteria (mean age 57 ± 13, female 38.4 %, mean disease duration 13.9 ± 8.6 years, peripheral disease 83.8 %, axial manifestations 34.5 %, radiological erosive disease 49 %) compared with 248 controls of the same ethnic origin matched for age and sex. The presence of axial disease was defined by the clinical axial involvement and/or the presence of radiological alteration consistent with spondyloarthropathy according to New York criteria. The presence of peripheral disease (arthritis and/or enthesitis) was defined only on clinical basis. A total of 40 SNPs, mapping within the genes mentioned above, were genotyped in both groups and used to perform association analyses by subdividing the PsA sample into subgroups according to different clinical manifestations on the basis of axial and peripheral involvements. No differences between patients and controls were found in the distribution of the IL-17A, IL17-RA, IL-23A and IL-23R genes allelic variants. Comparing patients with axial disease versus those without, we found that axial manifestations were significantly associated with the presence of IL-23R rs12401432 GG homozygosity (26.8 % vs. 5.3 %, p corr = 0.019, OR 2.63 [95 % CI 1.13-6.16]). No differences in distribution of the allelic variants were found comparing patients with versus those without peripheral disease or patients with versus without radiological peripheral erosions. In PA patients of northern Italian origin, IL-17A, IL17-RA, IL-23A and IL-23R genes allelic variants are not associated with disease susceptibility. However, a strong association with the IL-23RA rs12401432 GG genotype is associated with axial involvement of the disease.