YKL‐40: The Search for New Biomarkers in Rheumatoid Arthritis

There is a need for biomarkers to detect early joint inflammation and destruction of cartilage in different types of arthritis. YKL‐40, a 39 kDa heparin‐ and chitin‐binding secreted glycoprotein (also known as human cartilage gp39), has been recently discovered. Its exact biological function is still unclear. Specific receptors for YKL‐40 have not been identified yet. The clinical significance of YKL‐40 as a biomarker is discussed in different aspects. High level of YKL‐40 is found in various human i`nflammatory and neoplastic diseases. We present a review highlighting the information available on YKL‐40 and its significance in inflammatory joint diseases, like rheumatoid arthritis (RA). We also report original personal data on the topic concerning YKL‐40 levels in serum and synovial fluid of patients with RA in comparison with ultrasonographic parameters and cytokine levels. The findings suggest that YKL‐40 might be implicated in the pathogenesis of the disease and could indicate the level of joint inflammation