Recently, NfL has been included as a biomarker of neurodegeneration in the diagnostic criteria for Alzheimer's disease [6], while in multiple sclerosis, regular monitoring of serum NfL levels has been proposed for its high prognostic value for subclinical disease activity, relapse risk, and the development of gadolinium‐enhancing lesions [7]. Here, NEFL is linked to early-onset autosomal dominant Alzheimer disease.