CHI3L1 (chitinase 3-like protein 1, human cartilage glycoprotein 39 (HC-gp39), YKL-40, gp38k, chondrex, breast regression protein 39 (BRP-39)) is up-regulated in inflamed tissues in ulcerative colitis, Crohn's disease, rheumatoid arthritis, osteoarthritis, asthma, chronic obstructive pulmonary disease (COPD) and liver cirrhosis, as well as in solid cancers [1-10]. Here, CHI3L1 is linked to rheumatoid arthritis.