Interestingly, Hinsinger et al. found that YKL-40 levels in serum and CSF increased with time; nonetheless, the study concerned mostly CIS (N = 40)/RRMS (N = 66) patients and only 16 PMS subjects, the follow-up was longer (≥2 years) and no information on the applied therapy was included in the article. Here, CHI3L1 is linked to premenstrual tension.