Elevated levels of tau in cerebrospinal fluid (CSF) are also seen in CJD and AD [8,9,10,11,12,13,14,15,16], but, unlike neurofilament (NfL), an elevation of CSF tau is not seen in most other neurodegenerative conditions [12,17,18]. The gene discussed is NEFL; the disease is Creutzfeldt Jacob disease.