Background Psoriatic arthritis (PsA) is a disease developed in 10-20% of psoriasis patients. HLA–Cw*06 has been identified as the major genetic determinant of susceptibility to psoriasis.
Objectives To estimate the prevalence of HLA-Cw6 and Cw7 in healthy population, patients with psoriasis without joint disease and patients with PsA and to analyze the influence of both alleles in the characteristics of PsA.
Methods Genotyping of HLA-Cw * 06 and * 07 was performed on DNA samples of 390 Caucasian subjects by PCR-SSP (Sequence specific primer). The allele frequencies of HLA-Cw * 06 and * 07 were determined in patients with psoriasis (n = 117), PsA (n = 172), and compared with those of healthy controls (n = 101), and we calculated the odds ratio and confidence interval of 95% (OR, 95% CI). We determined the association of alleles with clinical-radiological forms of PsA (peripheral and axial / mixed). We used the chi-square test, Fisher’s exact test and t Student. We consider to be significant at p <0.05.
Results The frequencies of HLA-Cw * 06 were higher in type 1 psoriasis (OR 7.1, 95% CI 1.8-27.9, P <0.0001) and PsA (OR 3.5, 95% CI 1.7-7.3, P 0.001) relative to healthy controls, thus, in HLA-Cw * 06 positive patients with psoriasis, the diagnosis was at younger ages, 19.4 years (SD 12.5) vs 34.8 (18.8), p <0.0001) but not in PsA (p 0.941); although PsA patients with type I psoriasis had been diagnosed before patients with type II psoriasis (40.0 years (12.2) vs 57.6 (9.7), p <0.0001) regardless of the alleles. HLA-Cw * 0602 was associated with type I psoriasis (OR 3.3, 95% CI 1.5-7.1, p 0003) and PsA (OR 3.5, 95% CI 1.7-7.3, p 0.001) compared to healthy controls, but there were no differences in the HLA-Cw * 0602 prevalence between clinical-radiological forms of APs neither in clinical and laboratory features, metrology and radiological damage. PsA patients with type I psoriasis had a higher prevalence of HLA-Cw * 0602 than PsA patients with type II psoriasis (p 0.001). No differences were observed for the HLA-Cw * 07 and its subtypes relative to healthy controls or patients with psoriasis.
Conclusions HLA-Cw * 06 and its main subtype * 0602, are more prevalent in our patients with cutaneous psoriasis and psoriatic arthritis compared with healthy controls, and are more frequent in patients with a diagnosis of an earlier age. There was no influence on other features analyzed in PsA patients We found no difference in HLA-Cw * 07.
Acknowledgements The authors thank José Luis Fernández-Sueiro for him hard work and dedication. Rest in peace.
Disclosure of Interest None Declared