CHI3L1 and myositis disease: Our aim was to evaluate if there is an association between the serum levels and muscle tissue expression of YKL-40 with clinical variables such age, IIM phenotype14, muscle strength trough Manual Muscle Testing 8 (MMT8)15, the clinical activity and disease damage using the myositis disease activity assessment (MYOACT) and muscle damage index (MDI), respectively16.