KIT and rheumatoid arthritis: Differences between UA evolving to RA or PsA (UA-RA vs. UA-PsA) were only found in CD117+ mast cells and Hsp47+ lining synovial fibroblasts densities, which were both higher in the UA-PsA group (p = 0.025 and p = 0.036, respectively) (Table 2 and Figure 2).