NfL in CSF increases in neurodegenerative diseases, such as Alzheimer disease, frontotemporal dementia, vascular dementia and even human-immunodeficiency virus associated cognitive impairment (Abu-Rumeileh et al., 2018; Anderson et al., 2018; Chatterjee et al., 2019; Martin et al., 2019). The gene discussed is NEFL; the disease is Cognitive impairment.