BLK and rheumatoid arthritis: In patients with ACPA-negative RA, certain polymorphisms have been identified, including variants in the ankyrin repeat domain 55(ANKRD55)/interleukin 6 signal transduce (IL6ST), B lymphoid tyrosine kinase (BLK), tumor necrosis factor alpha-induced protein 3 (TNFAIP3), GIN1 protein/C5orf30 (GIN1/C5orf30), STAT4, 60S ribosomal protein pseudogene (RPL), and nuclear factor I A (NFIA)genes, suggesting that distinct genetic factors may underlie these two subsets of RA (24, 25).