Characteristics of Patients with Hereditary Transthyretin Amyloid Polyneuropathy and Chronic Idiopathic Axonal Polyneuropathy in Russia: PRIMER Study Results

Introduction. Hereditary transthyretin amyloidosis with polyneuropathy (hATTR-PN) is a severe progressive hereditary disease. Even with the availability of genetic testing for transthyretin (TTR) gene variants, timely hATTR-PN diagnosis remains challenging due to a great variability in its clinical presentation. Patients with hATTR-PN are often misdiagnosed with chronic idiopathic axonal polyneuropathy (CIAP). The objective of our study is to describe the baseline electrophysiological, clinical, and demographic characteristics of hATTR-PN and CIAP patients and to establish patients' pre-selection criteria for genetic testing. Materials and methods. Retrospective analysis was performed in 42 hATTR-PN patients and 58 CIAP patients (according to diagnosis defined in medical records from 1 January 2017 to 1 March 2024). Demographic, clinical, and electrophysiological data were collected at diagnosis. To identify factors influencing the likelihood of the hATTR-PN presence, a logistic regression model including clinically relevant variables was developed. Results. The mean age of hATTR-PN and CIAP patients was 57.7 and 60.9 years, respectively. As compared with CIAP patients, those with hATTR-PN more frequently exhibited gait disturbances (64.3% vs 37.9%), autonomic (47.6% vs 12.1%), cardiac (35.7% vs 10.3%) and gastrointestinal symptoms (64.3% vs 12.1%), unintentional weight loss (45.2% vs 12.1%), and heart failure with preserved ejection fraction (26.2% vs 6.9%). Peripheral nerve conduction scores were also lower in the hATTR-PN group. In predicting hATTR-PN, the logistic regression model had a sensitivity of 91% and a specificity of 97%. Conclusion. Demographic, clinical, and electrophysiological characteristics of patients with hATTR-PN and CIAP were described. Based on the screening data, it is feasible to predict hATTR-PN in CIAP patients with relatively high accuracy, sensitivity, and specificity.