Detecting Polyneuropathy in Patients with Hereditary Transthyretin Amyloid Cardiomyopathy.

Background: Patients with hereditary transthyretin amyloid cardiomyopathy (hATTR-CM), can show neurologic signs that lead to the eventual onset of polyneuropathy (PN). Detection of PN among patients with hATTR-CM can identify candidates for disease-modifying therapies that could significantly reduce the incidence of mortality and morbidity for these complex patients. The purpose of this study is to determine the prevalence of PN among patients with hATTR-CM. Methods: Sixty patients with hATTR-CM were enrolled in this prospective study, from the Amyloidosis Clinic at the University Health Network in Toronto, Ontario, Canada. All patients (average age: 69.12 ± 11.82 years; 51.7% male; 48.3% female) were referred to neurology programs specialized in hATTR PN. Comprehensive neurologic assessments were conducted, including a physical examination and nerve conduction studies (NCSs). NCSs were performed on the upper and lower extremities. Results: Thirty patients (50.0%) displayed clinical and NCS abnormalities. Six patients (10.0%) did not display any neurologic abnormalities on the physical examination, but did have abnormalities on the NCSs, suggesting the presence of transthyretin-PN. The abnormalities on the NCSs were more indicative of sensory PN than of motor polyneuropathy. Twenty-four patients (40.0%) did not display any clinical or NCS abnormalities. Based on the systematic neurologic assessment, 36 patients in our study were identified as having a mixed hATTR phenotype, and they are to receive specific disease-modifying therapies, either patisiran or inotersen. Conclusion: Patients with hATTR-CM should be systematically referred to a specialized neurologist for routine assessment, especially patients who report neurologic symptoms (ie, numbness and burning sensation in extremities).