Elevated serum concentrations of YKL-40 are seen in patients with several different diseases, but all are characterised by inflammation and ongoing tissue remodelling, for example, ischemic cardiovascular diseases, cancer, diabetes, COPD, rheumatoid arthritis, inflammatory bowel disease, pneumonia, and liver fibrosis (37–41). Here, CHI3L1 is linked to chronic obstructive pulmonary disease.