High levels of cerebrospinal fluid free kappa chains predict conversion to multiple sclerosis

► Some clinically isolated syndrome (CIS) patients develop multiple sclerosis (MS). ► The identification of CIS patients at MS risk is crucial as early treatment improves their outcome. ► Inflammatory demyelination is a hallmark of MS. ► High cerebrospinal fluid (CSF) free kappa chains (FKC) reflect local inflammation. ► CSF FKC levels above 0.53 mg/l predict MS conversion in CIS patients (p < 0.0001).