Geographical Disparities in the Detection and Certification of Systemic Amyloidosis in Japan: A Nationwide Registry...

Systemic amyloidosis has long been considered a rare disease, yet its nationwide epidemiology in Japan remains incompletely characterized, particularly with respect to geographical variation.

We analyzed publicly available data from Japan's national intractable disease registry (Designated Disease 28: systemic amyloidosis), which includes systemic AL/AH amyloidosis, wild-type and variant transthyretin amyloidosis, and other hereditary systemic forms, from 2015 to 2024. Annual prefecture-level counts of certified patients were extracted. Population-adjusted rates were calculated as the number of patients per 10,000 population using the 2020 national census as a fixed denominator. The total number of registered patients increased from 2,304 in 2015 to 8,168 in 2024, representing a 3.5-fold rise. The nationwide population-adjusted rate increased from 0.18 to 0.65 per 10,000 population. Marked geographical disparities were observed, with a pronounced west-east gradient and consistently higher rates in western Japan. In 2024, Oita Prefecture had the highest rate (2.2 per 10,000 population), followed by Kumamoto, Kochi, Nagano, Ehime, and Fukuoka.

Registered systemic amyloidosis cases in Japan increased substantially over the past decade, particularly after the approval of tafamidis for transthyretin amyloid cardiomyopathy in 2019. The persistent geographical disparities may reflect differences in diagnostic practice and certification processes rather than true variation in disease prevalence, suggesting that systemic amyloidosis may remain incompletely recognized nationwide.