In 2020, Kim et al. assessed VEGF, placenta growth factor (PlGF), sFlt-1, and IL-6 levels in the synovial fluid and/or serum of patients with RA, and analyzed their possible correlations with US assessment of synovitis, as well as with therapeutic responses to csDMARDs versus bDMARDs. Here, PGF is linked to rheumatoid arthritis.