Neurofilament light chain (NfL), as a constituent of the neuronal cytoskeleton, is a robust, well-known biomarker specific for neuroaxonal damage and has diagnostic and prognostic value in various neurological disorders such as amyotrophic lateral sclerosis, frontotemporal dementia, multiple sclerosis, or stroke [5–9]. The gene discussed is NEFL; the disease is amyotrophic lateral sclerosis.