Early on a markedly increased CSF levels of NfL in frontotemporal dementia (FTD) as compared with controls and Alzheimer ́s disease was found [6], a finding valid also for NfL in blood [7], and increased peripheral NfL has now been reliably validated in FTD [8–13]. The gene discussed is NEFL; the disease is early-onset autosomal dominant Alzheimer disease.