Compared with psoriatic arthritis (PsA), RA synovial membranes contain fewer vessels, lower lipid content, and fewer neutrophils, mast cells, CD163+, and CD117+ cells, with equal levels of lining and sublining CD68+ cells, sublining CD3+, CD20+, and CD21+ cells, but higher levels of CD138+ cells, and these differences appear to be independent of therapy (26, 45, 46). This evidence concerns the gene CD68 and rheumatoid arthritis.