Longitudinal multimodal assessment of peripheral nerve involvement in wild-type transthyretin amyloidosis

Wild-type transthyretin amyloidosis (ATTRwt) is a progressive disease marked by extracellular transthyretin amyloid deposition, predominantly causing cardiomyopathy. Neurological manifestations are known in hereditary ATTR but remain comparatively understudied in ATTRwt.

Patients with ATTRwt cardiomyopathy were prospectively evaluated at baseline and after 1 year, alongside healthy controls. Neurological assessment included Neuropathy Impairment Score Lower Limb (NIS-LL), nerve conduction studies, quantitative sensory testing (QST), serum neurofilament light chain (sNfL), and intra-epidermal nerve fiber density (IENFD) from skin biopsies. Symptoms and fatigue were assessed using Norfolk-QoL-DN and Chalder Fatigue scale.

Twenty-three patients were included and compared to controls. Pathological IENFD occurred in 47.8% of patients vs. 4.3% of controls (p=0.002). In ATTRwt, except cold detection, all QST parameters were abnormal. Sensory-predominant axonal polyneuropathy was present in 82.6%, with higher NIS-LL and symptom burden (p<0.001). sNfL levels were similar between groups. Carpal tunnel syndrome was frequent (82.7%). Polyneuropathy with CTS was more common in ATTRwt (p=0.025). At follow-up, we observed no clinical or electrophysiological progression, and no newly diagnosed cases of polyneuropathy.

ATTRwt is associated with mixed fiber neuropathy and frequent entrapment neuropathies which should raise suspicion for ATTRwt. We found subtle clinical progression over 13 months.