The CLEC12A gene codes for an immune inhibitory receptor that maps to 12p13.2. Since an increase in CLEC12A mRNA correlates with rheumatoid factor values greater than 40IU/ml in rheumatoid fibroblast-like synovial cells, this study assessed the potential of an association between CLEC12A and rheumatoid arthritis (RA) using a phenotype-based approach.

A discovery cohort of Western European ethnicity was genotyped for eight tag single nucleotide polymorphisms. Statistical analyses relied on the transmission disequilibrium test, relative risk and 95% confidence interval (CI) calculations. Observed haplotype frequencies were compared to expected frequencies using a family-based association test. Statistically significant associations were further tested in a second cohort of unrelated West-European RA patients.

An overtransmission of the C allele of the rs1323461 tag single nucleotide polymorphism was observed (56.6% of allele C transmission, P=0.046) in the discovery cohort. The relative risk of the AC and CC genotypes when compared to the AA genotype was high (relative risk=4.08; 95% CI: 1.52–10.95, uncorrected P=2.1×10⁻³), particularly in the subgroup of erosive RA (relative risk=5.27; 95% CI: 1.53–18.19, uncorrected P=2.1×10⁻³), both remaining statistically significant after conservative Bonferroni’s correction. The CGAGCCGA haplotype was observed more frequently than expected (P=0.013). In the second cohort, the C allele had a tendency to be more frequent in RA patients (82.4%) than controls (79.2%) (P=0.069).

We report a potential genetic association of CLEC12A with RA. Since CLEC12A encodes for the myeloid inhibitory C-type lectin-like receptor that modulates cytokine synthesis, this receptor may contribute to the pathogenesis of RA.