CHI3L1 and rheumatoid arthritis: As mentioned earlier, several biological effects of YKL-40 are known such as inflammation and tissue remodeling as well as its main sources, highlighting its exacerbated expression in inflammatory diseases such RA or SLE, however; some researchers has pointed out that this expression can vary according disease type which could be due to the multiorgan damage in IIM compared with RA where the damage is directed against joints mainly19,24.