Association of MICA alleles with psoriatic arthritis and its clinical forms. A multicenter Italian study.

OBJECTIVE Analysis of the association between psoriatic arthritis (PsA) clinical forms and MICA gene transmembrane polymorphisms. METHODS Patients were classified as having peripheral asymmetric oligoarthritis (AO), peripheral symmetric poly-arthritis (PA) and spondylitis (SP), or disease combinations (PA/SP, OA/SP). Two hundred and twenty-six patients with PsA were typed for MICA exon 5 microsatellite (TM) by heteroduplex analysis and compared with 225 normal controls. RESULTS MICA-TM microsatellite typing revealed that, among the different clinical forms of PsA, only the combined PA/SP subset shows a significant positive association with MICA-A9 and a lower frequency of MICA-A4, A5 genotype in PsA patients with a decrease, only in the PA/SP cohort, of all MICA-A5 combinations except MICA-A5, -A9. CONCLUSION These results suggest a role for genes within the HLA region in the pathogenesis of PsA, and reinforce the idea that the different forms of PsA may have heterogeneous genetic basis.