ANKHand Susceptibility to and Severity of Ankylosing Spondylitis

Objective.Unconfirmed reports describe association of ankylosing spondylitis (AS) with several candidate genes includingANKH. Cellular export of inorganic pyrophosphate is regulated by the ANK protein, and mutant mice (ank/ank), which have a premature stop codon in the 3’ end of theankgene, develop severe ankylosis. We tested the association between single-nucleotide polymorphisms (SNP) in these genes and susceptibility to AS in a population of patients with AS. We investigated the role of these genes in terms of functional (BASFI) and metrological (BASMI) measures, and the association with radiological severity (mSASSS).Methods.Our study was conducted on 355 patients with AS and 95 ethnically matched healthy controls. AS was defined according to the modified New York criteria. Four SNP inANKH(rs27356, rs26307, rs25957, and rs28006) were genotyped. Association analysis was performed using Cochrane-Armitage and linear regression tests for dichotomous and quantitative variables. Analyses of Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), BASFI, and mSASSS were controlled for sex and disease duration.Results.None of the 4 markers showed significant single-locus disease associations (p > 0.05), suggesting thatANKHwas not a major determinant of AS susceptibility in our population. No association was observed between these SNP and age at symptom onset, BASDAI, BASFI, BASMI, or mSASSS.Conclusion.These results confirm data in white Europeans thatANKHis probably not a major determinant of susceptibility to AS.ANKHpolymorphisms do not markedly influence AS disease severity, as measured by BASMI and mSASSS.