engleski

Association of mica microsatellite polymorphism with psoriatic arthritis in the Croatian population

Psoriatic arthritis (PsA) is an inflammatory arthritis that usually follows the onset of psoriasis and it is in the most cases negative for the rheumatoid factor. We previously reported about association between HLA-B*39 and -B*57 alleles with psoriatic arthritis in the Croatian population. However, it has not yet been clarified whether HLA-B alleles itself are pathogenic genes related to PsA or is there some other gene in linkage disequilibrium with these two HLA-B alleles. Recently, the triplet repeat (GCT/AGC) polymorphism in transmembrane region of the MHC class I chain related A (MICA) gene was found to be associated with different diseases. To clarify the role of MICA polymorphism in PsA susceptibility, we have studied the distribution of MICA alleles in 55 /28 male and 27 female) Croatian PsA patients and 156 healthy controls in relation to the presence of HLA-B*39 and B*57 alleles. The MICA polymorphism was determined by PCR and electrophoresis on 6% polyacrylamide gel in an automated sequencer (ALFexpress). The MICA-A4 allele (relative risk, RR=2.1, pcorr=0.0171), B*39 (RR=9.2, pcorr=0.00068) and B*57 (RR=8.4, pcorr=0.0087) were significantly increased in the Croatian patients with PsA. The frequency of MICA-A9 allele was similar in both groups.We did not observe linkage disequlibrium between MICA-A4 and those two associated HLA-B alleles. Stratification analysis showed significant association between MICA-A4 allele and PsA susceptibility in B*39 negative subgroup of PsA patients (RR=2.4, p=0.01795) as well s in B*57 negative subgroup of patients (RR=2.4, p=0.01303). The level of significance was not increased with respect to that observed between B*39 and PsA as well as between B*57 and PsA alone. On the base of these findings we concluded that MICA polymorphism in combination with HLA-B alleles is a useful susceptibility marker of PsA, specially in the B*39 and B*57 negative patients.

MICA; PsA; HLA; Croatians

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