LRG is a novel inflammatory marker clinically useful for the evaluation of disease activity in rheumatoid arthritis and inflammatory bowel disease.

By proteomic screening of sera obtained from patients with rheumatoid arthritis (RA), we previously identified leucine rich α2 glycoprotein (LRG) as a possible marker for inflammation. Unlike C-reactive protein (CRP), a biomarker widely used to evaluate inflammation, LRG is induced not only by IL-6 but also by other proinflammatory cytokines. In addition, LRG is upregulated not only in liver but also in local inflammatory sites. Therefore, serum LRG is a novel inflammatory marker applicable to evaluate inflammation in many diseases including ulcerative colitis in which serum CRP often fails to reflect disease activity and RA to which IL-6-blocking biologic agents such as tocilizumab are given as a first line therapy. Interestingly, evidence indicates that LRG is functionally involved in pathogenesis of inflammation, by promoting cellular proliferation, differentiation and angiogenesis via modulating TGF-β signaling.