Three Newly Recognized Likely Pathogenic Gene Variants Associated with Hereditary Transthyretin Amyloidosis

Abstract

Introduction: Hereditary transthyretin amyloidosis (ATTRv [variant]) is a clinically heterogeneous, progressively debilitating, fatal disease resulting from the deposition of insoluble amyloid fibrils in various organs and tissues. Early diagnosis of ATTRv can be facilitated with genetic testing; however, such testing of the TTR gene identifies variants of uncertain significance (VUS) in a minority of cases, a small percentage of which have the potential to be pathogenic. The Akcea/Ambry VUS Initiative is dedicated to gathering molecular, clinical, and inheritance data for each TTR VUS identified by genetic testing programs to reclassify TTR variants to a clinically actionable status (e.g., variant likely pathogenic [VLP]) where appropriate. Methods: Classification criteria used here, based on recommendations from the American College of Medical Genetics and Genomics, are stringent and comprehensive, requiring distinct lines of evidence supporting pathogenesis. Results: Three TTR variants have been reclassified from VUS to VLP, including c.194C>T (p.A65V), c.172G>C (p.D58H), and c.239C>T (p.T80I). In each case, the totality of genetic, structural, and clinical evidence provided strong support for pathogenicity. Conclusions: Based on several lines of evidence, three TTR VUS were reclassified as VLP, resulting in a high likelihood of disease diagnosis for those and subsequent patients as well as at-risk family members.