In MS, there is evidence that serum NfL (sNfL) levels correlate with CSF NfL, are associated with clinico‐radiological inflammatory disease activity, disability progression, and brain atrophy, and are modulated by disease‐modifying therapies (DMTs).3, 5, 6, 7, 8, 9. This evidence concerns the gene NEFL and myeloid sarcoma.