This meta-analysis showed that the MICA-TM A9 allele is associated with psoriasis susceptibility in Asian populations and that the MICA-TM A9 allele is associated with a PsA risk in Europeans.
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.
The MICA-A9 allele of the transmembrane microsatelite MICA polymorphism occurred more frequently in PsA with psoriasis type II group (age of psoriasis onset after 40 years) than in controls, 58.6 versus 38.0%, respectively however, this finding did not reach a statistical significance after correction (P (corrected) = 0.085).
These results suggest that the MICA gene or other nearby gene(s) may be involved in the development of PsA, and it would thus appear that psoriasis vulgaris (PsV) and PsA are associated with different MHC susceptibility genes.