Atypical AA amyloid deposits in bovine AA amyloidosis.

In bovine amyloid protein A (AA) amyloidosis, amyloid deposits are typically observed in the kidney and spleen at necropsy. To determine the distribution of amyloid deposits in cows affected with AA amyloidosis, we examined organs known to be sites of amyloid deposits that are also processed for human consumption in 14 cows: 11 with typical clinical symptoms (typical amyloidosis) and three with no typical clinical symptoms (atypical amyloidosis). We found unusually high amounts of amyloid deposits in the tongue and other organs in all 14 cows regardless of the presence or absence of clinical amyloidosis symptoms. Cows with typical amyloidosis had heavier amyloid deposits in the spleen and renal glomeruli than cows with atypical amyloidosis. From clinical symptoms and histological examinations, we found that cows with typical and atypical amyloidosis can be classified into two groups, class I and class II, according to the presence or absence of heavy amyloid deposits in the spleen and renal glomeruli. However, no significant differences were observed between the amyloid fibrils of class I and class II amyloidosis by electron microscopy and Western blot analysis.