Senescence Accelerates the Occurrence of Dual Amyloidosis: Alzheimer's Disease and Wild-Type Transthyretin Amyloidosis

We report a case of dual amyloidosis with Alzheimer's disease and wild-type transthyretin (ATTRwt) amyloidosis. A 76-year-old man with Alzheimer's disease was referred for anti-amyloid-β therapy with lecanemab. He also had symptoms of congestive heart failure and a history of carpal tunnel syndrome, cubital tunnel syndrome, and lumbar spinal stenosis; raising Technetium-99m pyrophosphate myocardial scintigraphy showed abnormal uptake, and histopathologic examination revealed transthyretin (TTR) amyloid deposition in both myocardial and gastrointestinal biopsy specimens. Genetic testing for the <i>TTR</i> gene revealed no variants. The diagnosis of ATTRwt amyloidosis was confirmed, and treatment with a TTR tetramer stabilizer, tafamidis, was initiated. Alzheimer's disease of the brain and ATTRwt amyloidosis of the heart are both representative amyloidoses associated with aging. To date, there are no reported cases of dual amyloidosis other than autopsy cases, but considering the high prevalence of both diseases, it is plausible that a significant number of elderly individuals may suffer from both diseases simultaneously but are underdiagnosed. In recent years, disease-modifying drugs effective against both diseases have become available, making early diagnosis increasingly important.