Distribution of HLA-B27 subtypes in Sardinia and continental Italy and their association with spondylarthropathies.

We analyzed a large cohort of patients from Sardinia and continental Italy with 2 forms of spondylarthropathy: AS (271 patients), and PsA (263 patients). Patients with AS were selected based on fulfillment of the modified New York criteria, and PsA was diagnosed according to the Moll and Wright criteria. Patients and controls were recruited, via a program in conjunction with the Italian Ministry of Education, from several regions of Italy; all gave informed consent. Some of the patients and controls from Sardinia have been described in another report. B27 subtyping was performed using the HLA–B27 high resolution kit.our findings in an analysis of the HLA–B27 subtype distribution in a large cohort of patients with either AS or PsA confirm our previous observation that B*2709 is never found in patients with AS. Whether this allele plays a protective role in the pathogenesis of AS cannot be formally assessed due to the low number of B*2705/09 heterozygotes in Sardinia. However, the latter hypothesis should be considered since, if this allele were neutral, occasional B*2709 positivity among patients with AS would probably have been identified by now. The recently reported differences in the antigen-presenting properties of B*2709 versus B*2705 molecules, and/or in the haplotypes harboring B*2705 and B*2709 alleles, offer new frameworks for considering the differential association of the 2 alleles with AS.