Systemic fibrinogen Aα-chain amyloidosis in a blue-winged kookaburra (Dacelo leachii): The first non-AA systemic amyloidosis in avians.

Amyloidosis is a group of protein-misfolding disorders characterized by the deposition of insoluble fibrils in tissues. In birds, only systemic amyloid A (AA) amyloidosis and cerebral Aβ amyloidosis have been described to date, and non-AA systemic amyloidosis has not been reported. We describe the first case of non-AA systemic amyloidosis in an avian species, fibrinogen Aα-chain (FibA) amyloidosis, in an 8-year-old male blue-winged kookaburra (Dacelo leachii). Histologically, prominent amyloid deposits were observed in renal glomeruli and in arterial walls of multiple organs. Ultrastructurally, amyloid deposits consisted of non-branching fibrils. Amyloid isolated from multiple organs was consistently identified as FibA-derived by liquid chromatography-tandem mass spectrometry using a customized protein database constructed from hepatic transcriptomic data, enabling amyloid typing in a species lacking comprehensive genomic resources. Peptide mapping demonstrated predominant involvement of the FibA αC-connector region, which was further supported by immunohistochemical labeling of amyloid deposits with an antibody against this region. This case expands the spectrum of avian amyloidosis and highlights the evolutionarily conserved amyloidogenic vulnerability of FibA across vertebrate species.