It is difficult to say that there is more evidence for cardiac amyloidosis (CA) than for ischemic heart disease. On the other hand, 99 m technetium pyrophosphate ( 99 m Tc-PYP) scintigraphy has been reported to be useful with high sensitivity and specificity, especially in transthyretin (TTR) amyloidosis (ATTR) 1,2 Due to the spread of diagnosis using this method, CA, especially wild-type ATTR (ATTRwt) amyloidosis, which has traditionally been considered a rare disease, is more prevalent than previously assumed, and encountered relatively frequently in daily clinical practice. Furthermore, treatment for not only amyloid light-chain (AL) amyloidosis, but also ATTR, has also progressed rapidly. Tafamidis, a drug that stabilizes the TTR tetramer and suppresses amyloid fibril formation and tissue deposition, was listed and used in Japan in November 2013 for the treatment of peripheral neuropathy in patients with hereditary (variant) ATTR (ATTRv) amyloidosis. In addition, following the results of the 2018 Transthyretin Amyloidosis Cardiomyopathy Clinical Trial (ATTR-ACT), which showed the efficacy of tafamidis for CA, 3 the use of TTR to treat CA was approved in March 2019 in Japan.Needless to say, amyloidosis is a systemic disease, and in Japan, numerous studies have been conducted and medical treatments devised by the Ministry of Health, Labour and Welfare (MHLW)'s "Research Group on Amyloidosis", a research project on intractable disease policy. The present guidelines have been developed in coordination between the MHLW's "Research Group on Amyloidosis", the Japanese Circulation Society (JCS) and cardiology-related societies, the Japanese Society of Amyloidosis, and the Japanese Society of Hematology. Systemic amyloidosis specified by the MHLW as being an incurable disease is classified into the following four types.

These findings suggest that direct insult of amyloid fibrils causes Schwann cell damage, resulting in the predominant loss of small-fiber axons characteristic of early-onset cases. In addition, vasculopathy may participate in the pathogenesis of neuropathy, particularly in late-onset cases.

Amyloidosis is a protein conformational disorder with the distinctive feature of extracellular accumulation of amyloid fibrils that come from different proteins. In the ligamentum flavum of the lumbar spine, amyloid deposits were frequently found in elderly patients with lumbar spinal canal stenosis and were at least partially formed by wild-type transthyretin. However, how amyloid deposits in the ligamentum flavum affect lumbar spinal canal stenosis has remained unclear. In this study, we analyzed clinical, pathologic, and radiologic findings of patients with lumbar spinal canal stenosis who had amyloid deposits in the ligamentum flavum. We studied 95 ligamentum flavum specimens obtained from 56 patients with lumbar spinal canal stenosis and 21 ligamentum flavum specimens obtained from 19 patients with lumbar disk herniation. We evaluated histopathologic findings and clinicoradiologic manifestations, such as thickness of the ligamentum flavum and lumbar spinal segmental instability. We found that all 95 ligamentum flavum specimens resected from patients with lumbar spinal canal stenosis had amyloid deposits, which we classified into two types, transthyretin-positive and transthyretinnegative, and that transthyretin amyloid formation in the ligamentum flavum of patients with lumbar spinal canal stenosis was an age-associated phenomenon. The amount of amyloid in the ligamentum flavum was related to clinical manifestations of lumbar spinal canal stenosis, such as thickness of the ligamentum flavum and lumbar spinal segmental instability, in the patients with lumbar spinal canal stenosis with transthyretin-positive amyloid deposits. To our knowledge, this report is the first to show clinicopathologic correlations in transthyretin amyloid deposits of the ligamentum flavum. In conclusion, transthyretin amyloid deposits in the ligamentum flavum may be related to the pathogenesis of lumbar spinal canal stenosis in elderly patients.

This study provides Class III evidence that liver transplantation prolongs survival in patients with FAP Val30Met.