In this manner, BLK rs13277113A appears to belong to a haplotype associated with RA, such as the BLK rs922483 variant (which is in high LD; r2 > 0.7 with both BLK rs13277113 and rs2736340T/C), which affects the BLK mRNA and protein expression early in B cell ontogeny (Simpfendorfer et al., 2012). This evidence concerns the gene BLK and rheumatoid arthritis.