C9orf72 and amyotrophic lateral sclerosis: In the seminal work of Benatar et al. [85], pre-symptomatic carriers of known disease-causing mutations (e.g. SOD1, C9orf72, TARDBP, FUS, VCP) showed rising levels of serum NfL up to 11.6 months before “phenoconversion” (i.e., the onset of motor symptoms typical of ALS).