While the turnover of Nf-L in normally aging brains is slow, abnormally elevated levels of Nf-L in CSF and blood have been associated with several neurodegenerative conditions such as multiple sclerosis (MS), various types of dementia such as Alzheimer’s disease (AD) and frontotemporal dementia (FTD), and several other neurodegenerative diseases [4,6,8]. The gene discussed is NEFL; the disease is Alzheimer disease.