CHI3L1 and multiple sclerosis: Neurofilament light protein (NFL), a cytoskeletal polypeptide of the axon (1), and chitinase 3-like 1 (CHI3L1- also known as YKL40 or gp39), a glycoprotein secreted by activated glia in the central nervous system (CNS) (2), have both shown to be biomarkers of axonal destruction, and inflammation in multiple sclerosis (MS), respectively.