Longitudinal analysis of serum neurofilament light chain levels as marker for neuronal damage in hereditary transthyretin amyloidosis

To evaluate serum neurofilament light chain (sNfL) as biomarker of disease onset, progression and treatment effect in hereditary transthyretin (ATTRv) amyloidosis patients and <i>TTR</i> variant (<i>TTR</i>v) carriers. sNfL levels were assessed longitudinally in persistently asymptomatic <i>TTR</i>v carriers (<i>N</i> = 12), persistently asymptomatic ATTRv amyloidosis patients (defined as asymptomatic patients but with amyloid detectable in subcutaneous abdominal fat tissue) (<i>N</i> = 8), in <i>TTR</i>v carriers who developed polyneuropathy (<i>N</i> = 7) and in ATTRv amyloidosis patients with polyneuropathy on treatment (TTR-stabiliser (<i>N</i> = 20) or TTR-silencer (<i>N</i> = 18)). Polyneuropathy was confirmed by nerve conduction studies or quantitative sensory testing. sNfL was analysed using a single-molecule array assay. sNfL increased over 2 years in persistently asymptomatic ATTRv amyloidosis patients, but did not change in persistently asymptomatic <i>TTR</i>v carriers. In all <i>TTR</i>v carriers who developed polyneuropathy, sNfL increased from 8.4 to 49.8 pg/mL before the onset of symptoms and before polyneuropathy could be confirmed neurophysiologically. In symptomatic ATTRv amyloidosis patients on a TTR-stabiliser, sNfL remained stable over 2 years. In patients on a TTR-silencer, sNfL decreased after 1 year of treatment. sNfL is a biomarker of early neuronal damage in ATTRv amyloidosis already before the onset of polyneuropathy. Current data support the use of sNfL in screening asymptomatic <i>TTR</i>v carriers and in monitoring of disease progression and treatment effect.