In asymptomatic carriers of SOD1 and C9ORF72 mutations, Nfs increases both in CSF and in serum, prior to phenoconversion, confirm that increases in Nfs are already measurable early in the disease course of genetic ALS, and do not differ based on El Escorial diagnostic categories, highlighting the role of these biomarkers in early diagnosis [66,68,69,70,71]. The gene discussed is SOD1; the disease is amyotrophic lateral sclerosis.