Neurofilament light chain is a well-known marker for axonal–neuronal degeneration with, on the one hand, low specificity for the underlying pathomechanisms except for Tar-DNA-binding protein with 43 kDa induced neurodegeneration such as in ALS (Weydt et al., 2016; Goossens et al., 2018; Körtvelyessy et al., 2018; Bridel et al., 2019). The gene discussed is NEFL; the disease is amyotrophic lateral sclerosis.