Conclusions
In summary, our study demonstrated that the ERAP1 is significantly hypermethylated in AS patients, and the result is also verified by the lower mRNA level of AS patients. Our findings suggested that aberrant methylation of ERAP1 promoter may take part in the pathogenesis of AS and can be considered as diagnostic tool and therapeutic target of AS. The finding that NSAIDs use could alter the methylation level indicated that the efficacy of NSAIDs on AS could be through altering the methylation level of corresponding genes in some extent.