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

Analysis of the association between psoriatic arthritis (PsA) clinical forms and MICA gene transmembrane polymorphisms. 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. 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. 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.