Primary diffuse tracheobronchial amyloidosis in a dog.

Primary diffuse tracheobronchial amyloidosis was diagnosed at necropsy in an intact male Akita dog aged 11 years, a non-productive chronic cough having been the only related clinical sign. Histologically, eosinophilic hyalinized deposits were found as a band in the lamina propria underneath the epithelium of the trachea and bronchi. When stained with Congo red, apple-green birefringence was observed in the deposits viewed with polarized light. The amyloid did not lose sensitivity to Congo red staining after incubation with potassium permanganate, indicating that it was of the AL (amyloid light chain) type. Ultrastructural features of the amyloid included a typical fibrillar meshwork with individual fibrils measuring 9.5 to 10.5 nm in diameter. This is the first report of primary diffuse tracheobronchial amyloidosis in the dog.