CTSD and rheumatoid arthritis: M-CSF also contributes to the pathogenesis of RA through up regulation of neutrophil gelatinase-associated lipocalin (NGAL) in neutrophils, followed by induction of transitional endoplasmic reticulum ATPase (TERA), cathepsin D and transglutaminase 2(TG2) in synoviocytes [39].