Background HLA-Cw6 has been found to be associated with early onset psoriasis (PSO) type I. Psoriatic arthritis (PsA) is an inflammatory arthritis with psoriasis. The main feature of PsA is peripheral arthritis or axial manifestation. The arthritis usually follows the diagnosis of psoriasis by about 10 years. PsA is a complex genetic disorder that results from an interplay between multiple genetic environmental factors. The exact pathogenesis of PsA is unclear.

Objectives The aim of the study was to assess the significance of the association between the HLA-C*06 and PsA.

Methods The study group consisted of 50 patients with PsA (32 men and 18 women) hospitalized at the Rheumatology Clinic of Medical University in Wroclaw, Poland, in 2012. The median age of patients was 45 years. PsA was diagnosed by the criteria recommended by CASPAR group. The average duration of PsA and PSO was 7 and 15 years, respectively.

The patients were typed for the HLA-C alleles using HLA Ready Gene C low kit (Inno-train Diagnostik GmbH, Germany). DNA was extracted from peripheral blood taken on EDTA using Maxwell 16 Blood DNA Purification Kit (Promega Corp., USA) following the recommendation of the manufacturer.

Results HLA-C*06 was detected in 26 out of 50 patients (52%). The frequency of HLA-C*06 among PsA patients was significantly higher (26/50 vs. 36/123, OR=5.24, p<0.001) than those described for Polish healthy population [Łuszczek et al. Immunol Lett 2002 and Szczekowska Dobosz et al. Int J Immunogenet 2005]. Among 26 patients with HLA-C*06, 22 patients (85%) had polyarthritis (22/26 vs. 15/24 HLA-C*06, p=0.08) while among 4 patients presented with spondyloarthritis only one was carrying HLA-C*06 (1/4 vs. 25/46, ns).

Eighteen (36%) PsA patients presented with severe disease (PASI >10, BSA >10, more than five swollen and tender joints) and were subjected to anti-TNF-alpha therapy (adalimumab, etanercepet). Among those patients 14 were HLA-C*06 positive as compared to 12 patients out of 32 with less severe disease (14/18 vs. 12/32, p<0.01).

Conclusions Individuals carrying the HLA-C*06 alleles are five times more likely to develop PsA. HLA-C*06 positive PsA patients develop more severe disease (requiring anti-TNF-alpha treatment) and more frequently present with polyarticular pattern of PsA.

Our results confirm the association between HLA-C*06 allele and PsA and, furthermore, suggest that HLA-C*06 may be a prognostic factor of PsA severity.

Disclosure of Interest None Declared