Genetic association of htSNPs across the major histocompatibility complex with rheumatoid arthritis in an African-American population.

Notwithstanding the well-established association of HLA-DRB1 shared epitope alleles, interest remains in identifying additional major histocompatibility complex (MHC) region variants associated with rheumatoid arthritis (RA). We used a panel of 1201 haplotype-tagging single nucleotide polymorphisms (SNPs) designed for African Americans to find genetic variants associated with RA in a 3.8-Mb region encompassing the MHC. Conditioning on seven covariates, including HLA-DRB1 risk alleles and population structure, we identified an SNP in HLA-DOA (rs9276977) significantly associated with RA; minor allele frequency (MAF) 0.27 in cases versus 0.21 in controls, odds ratio (+/-95% confidence interval)=2.86 (1.61, 5.31). Genotyping of rs9276977 in an independent sample of African-American RA patients and controls did not replicate the association (MAF 0.28 in cases versus 0.27 in controls). This study points to the potential association of a SNP in the HLA-DOA gene with RA in African Americans, but also underscores the importance of replication of findings in larger patient cohorts.