An increase in the serum neurofilament light chain was shown to be related to the elevation of the CSF/serum quotient of albumin (Q Alb) and CSF-located CD80+ B cells and the presence of Gd-enhancement lesions on MRI, suggesting increased BBB permeability in MS [47], and treatment with disease-modifying therapies was found to decrease serum neurofilament light chain levels [47,48,49]. The gene discussed is NEFL; the disease is myeloid sarcoma.