AA-like amyloid deposits confined to arthritic joints in two dogs with rheumatoid arthritis

Two dogs with clinical, serological, radiographic and pathological changes similar to those of rheumatoid arthritis of man and a previously undescribed pattern of amyloid deposits are described. As revealed by light and electron microscopical investigations, amyloid fibrils were found exclusively in articular tissue structures of arthritic joints and in one tonsil of one dog. Based on our immunohistochemical results, the amyloid protein is believed to be of a local AA type.