First Japanese Case of Hereditary Transthyretin Amyloid Cardiomyopathy with an Ile68Leu Variant: A Case Report

Transthyretin amyloid cardiomyopathy (ATTR-CM) is increasingly recognized because of improved diagnostic modalities and disease-modifying therapy. We report the first Japanese case of hereditary ATTR-CM (ATTRv-CM) caused by the Ile68Leu variant, which has been previously described in European cohorts. A man in his 40s presented with heart failure and typical imaging findings of transthyretin amyloid cardiomyopathy (ATTR-CM). Genetic testing identified the Ile68Leu variant, which was absent in East Asian population databases. This case expands the genetic spectrum of ATTRv-CM in Japan and suggests that cardiac-predominant non-Val30Met TTR variants may occur in Japanese patients, with implications for the diagnosis, family counseling, and cascade screening in the future.