Moreover, other risk factors for MS development, including HLA DRB1 (human leukocyte antigen DRB1 locus gene) status (Huizinga et al., 2012[51]), immune response against EBV, and 25-hydroxycholecalciferol (25-hydroxy vitamin D3) (Sandberg et al., 2016[92]; Smolders et al., 2020[99]) have not been investigated in relation to NfL levels and the development of axonal injury. This evidence concerns the gene NEFL and myeloid sarcoma.