Sporadic Cardiac Amyloidosis by Amyloidogenic Transthyretin V122I Variant

Hereditary ATTR amyloid cardiomyopathy is defined as the intramyocardial deposition of amyloid fibrils derived from the mutation of transthyretin (TTR). A 51-year-old man was referred to our hospital for congestive heart failure. He and his family had no past history of heart diseases. Echocardiography showed remarkable left ventricular hypertrophy and reduced ejection fraction. Endomyocardial biopsy specimens presented positive staining of Congo-Red and transthyretin. A genetic test showed heterozygous V122I TTR gene mutation, which is very rare in Japan. We diagnosed him as with sporadic ATTR amyloidosis with mutation, and tafamidis was administered to stabilize TTR tetramer. Since the phenotype of ATTR amyloidosis varies depending on its penetration rate, it is crucial to always keep in mind the possibility of hereditary ATTR amyloidosis even in the case of amyloidosis with no clear family history.