However, NfL lacks disease specificity, as elevated levels are also observed with normal aging and across a range of neurodegenerative disorders, including multiple sclerosis (MS), Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), multiple system atrophy (MSA), and Parkinson’s disease (PD). The gene discussed is NEFL; the disease is Parkinson disease.