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Clinical presentation of systemic amyloidosis differs among subtypes, and accurate subtype classification is important for choosing the treatment. Amyloid transthyretin (ATTR) amyloidosis was the predominant among the recently consulted amyloidosis cases in Japan. To reveal the latest subtype frequency of systemic amyloidosis among autopsy cases in Japan. We analyzed systemic amyloidosis cases autopsied from January 2017 to December 2018, that were listed in the Annuals of the Pathological Autopsy Cases in Japan, Volumes 60 and 61. When the subtype was unclear, we performed a questionnaire survey, immunohistochemistry with in‐house rabbit polyclonal anti‐κ116–133, anti‐λ118–134, and anti‐transthyretin115–124 antibodies, and proteomic analysis. Out of 481 systemic amyloidosis cases listed in the Annuals, 411 cases were available for analysis (85.4%). We classified 399 of these systemic amyloidosis cases. ATTR was the most common subtype (44.4%, n = 177), followed by amyloid immunoglobulin light chain (AL) (38.8%, n = 155). Amyloid A and amyloid β2‐microglobulin were 9.3% (n = 37) and 6.0% (n = 24), respectively. Double deposition of amyloid was identified in 1.6% (n = 6). In 168 cases (42.1%), systemic amyloidosis was the main cause of death. Of these cases, AL was the most common subtype (47.6%, n = 80), followed by ATTR (41.1%, n = 69). ATTR is the most predominant subtype among the current autopsy cases in Japan. [ABSTRACT FROM AUTHOR]

An 85‐year‐old man with a history of aortic dissection suddenly fainted, underwent cardiac heart arrest, and died. An autopsy was performed, but the cause of death was not grossly identified. Congo red staining detected amyloid deposits in systemic organs, including the heart, lungs, liver, and kidneys. Immunohistochemical (IHC) analysis revealed immunoglobulin (Ig) λ light chain (‐λ) in systemic blood vessels and transthyretin (TTR) in the heart and lungs. Ig‐λ was predominantly positive in the blood vessels of the lungs, while TTR was detected in the alveolar septum. In the heart, Ig‐λ was positive in the endocardium and blood vessels, and TTR was positive in nodular deposits between cardiomyocytes. The concurrent deposition of Ig‐λ and TTR in the heart was further substantiated by laser microdissection (LMD)‐liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) at each deposition site. Despite systemic deposition of Ig‐λ, bone marrow biopsy findings were not diagnostic for multiple myeloma. In summary, we present an autopsy case of concurrent Ig‐λ and TTR deposition as revealed by IHC and LC‐MS/MS. When Congo red staining and IHC results are indeterminate due to the deposition of multiple amyloid proteins, LMD‐LC‐MS/MS is useful for determining the precursor protein. [ABSTRACT FROM AUTHOR]

Amyloidosis refers to a group of diseases with amyloid fibrils deposited in various organs and is classified into more than 30 diseases in humans based on the kind of amyloid protein. In order to elucidate the molecular pathogenesis of human amyloidosis, we studied the molecular mechanism of amyloid fibril formation in vitro. We first developed a novel fluorometric method to determine amyloid fibrils in vitro based on the unique characteristics of thioflavin T. We next proposed a nucleation-dependent polymerization model to explain the general mechanism of amyloid fibril formation in vitro. Based on this model, we characterized the biological molecular interactions that promote or inhibit amyloid fibril formation in vitro and developed models of pathological molecular environment for inducing human β2-microglobulin-related amyloidosis in long-term hemodialysis patients. We also proposed a novel and attractive cytotoxic mechanism of β2-microglobulin amyloid fibrils, that is, the disruption of endosomal/lysosomal membranes by endocytosed amyloid fibrils. These findings may be useful to elucidate the molecular pathogenesis of other kinds of human amyloidosis. [ABSTRACT FROM AUTHOR]