Inflammatory cytokines are implicated in the pathogenesis of giant cell arteritis (GCA) and polymyalgia rheumatica (PMR). In this study we have examined the potential association of a CA repeat polymorphism in the first intron of the interferon gamma (IFN-gamma) gene with disease susceptibility and clinical expression of these conditions.
Seventy-nine patients with isolated PMR, 59 biopsy-proven GCA patients and 129 ethnically matched controls from Lugo (NW Spain) were studied. Patients and controls were genotyped by molecular methods for the microsatellite dinucleotide (CA) repeat within the first intron of IFN-gamma gene.
No significant differences in the distribution of alleles for the IFN-gamma gene polymorphism between GCA and isolated PMR patients and controls were found. However, the frequency of IFN-gamma allele *4 (128 bp) was reduced in GCA patients (33.1%) compared with isolated PMR patients (46.2%). Also, GCA patients with visual ischemic manifestations exhibited a significantly reduced frequency of IFN-gamma allele *4 compared with those without visual manifestations (17.9% versus 42.5%; p = 0.05 [OR: 0.36, 95% CI: 0.13-1.00]). Moreover, allele *3 (126 bp) was over-represented in the GCA patients with visual ischemic manifestations (71.4% versus 44.4% in the remaining GCA patients; p = 0.01 [OR = 3.13, 95% CI: 1.27-7.68]).
In GCA, IFN-gamma functional polymorphisms are associated with clinical manifestations of severity rather than susceptibility to this vasculitis.