AbstractBackground and purposeHereditary transthyretin amyloidosis (ATTRv) is a life‐threatening disease caused by mutations in the gene encoding transthyretin (TTR). The recent therapeutic advances have underlined the importance of easily accessible, objective biomarkers of both disease onset and progression. Preliminary evidence suggests a potential role in this respect for neurofilament light chain (NfL). In this study, the aim was to determine serum NfL (sNfL) levels in a late‐onset ATTRv population and evaluate whether it might represent a reliable biomarker of disease onset (i.e., ‘conversion’ from the asymptomatic status to symptomatic disease in TTR mutation carriers).MethodsIn all, 111 individuals harbouring a pathogenic TTR variant (61 symptomatic ATTRv patients and 50 presymptomatic carriers) were consecutively enrolled. Fifty healthy volunteers were included as the control group. Ella™ apparatus was used to assess sNfL levels.ResultsSerum NfL levels were increased in ATTRv patients compared to both presymptomatic carriers and healthy controls, whilst not differing between carriers and healthy controls. An sNfL cut‐off of 37.10 pg/mL could discriminate between asymptomatic and symptomatic individuals with high diagnostic accuracy (area under the curve 0.958; p < 0.001), sensitivity (81.4%) and specificity (100%).ConclusionsSerum NfL seems to be a promising biomarker of peripheral nerve involvement in ATTRv amyloidosis and might become a reliable, objective measure to detect the transition from the presymptomatic stage to the onset of symptomatic disease. Further longitudinal studies are needed to confirm such a role and determine whether it could equally represent a biomarker of disease progression and response to therapy.