CTSB and rheumatoid arthritis: Interestingly, traits like platelet-to-lymphocyte ratio (Milovanovic et al., 2004; Zha et al., 2006; Fu et al., 2015; Gasparyan et al., 2019), sphingomyelin (Beckmann et al., 2017), cathepsin B (Ikeda et al., 2000; Behl et al., 2022), and LILRB2 protein levels (Huynh et al., 2007) have been positively associated with rheumatoid arthritis.