There is evidence that CHI3L1 levels are associated with CIS conversion to MS, disability progression (Cantó et al., 2011; Hinsinger et al., 2015; Håkansson et al., 2018; Huss et al., 2020), and presumably treatment response (Matute-Blanch et al., 2018). Here, CHI3L1 is linked to myeloid sarcoma.