In addition to the presence of oligoclonal bands and increased intrathecal IgG synthesis that are indicative of chronic immune activation and represent a key diagnostic tool in MS, numerous molecules have been examined, including markers of tissue damage, such as the neurofilament light chain (NfL), and other biomarkers reflecting either pathophysiological processes (demyelination, inflammation, and repair), or for improving diagnosis and predicting disease progression and clinical outcome. The gene discussed is NEFL; the disease is myeloid sarcoma.