Moreover, in our opinion, the decreased KDR protein expression in RA patients, associated with two functional KDR gene SNPs at position rs1870377T and rs2305948GG, appears to be due to lower affinity of VEGF to KDR, which results in dysfunctional KDR, higher affinity VEGF for FLT-1 or hypoxia-inducible factor (HIF)-1α, intensified angiogenesis, and a higher risk of RA, as well as higher disease activity in our patients. This evidence concerns the gene FLT1 and rheumatoid arthritis.