Familial renal amyloidosis in Abyssinian cats.

Medullary and glomerular amyloidosis, papillary necrosis, and secondary interstitial disease were diagnosed in eight related adult Abyssinian cats from two catteries. The lesions were similar to those in two unrelated mongrel cats with renal amyloidosis. Ultrastructurally, the patterns of amyloid deposition were as described in other species, although medullary deposition predominated. Potassium permanganate oxidation blocked Congo red staining of the deposits suggesting that they contained amyloid A protein (secondary amyloid). The disease may be a model of familial secondary amyloidosis and offers an opportunity to study the pathogenesis of both amyloid deposition and papillary necrosis. The histochemical characteristics of feline renal amyloid require careful attention to technique. Section thickness affects Congo red affinity and both dichroism as well as birefringence should be considered when interpreting staining reactions. Thioflavine-T may be the preferred stain for identification of small deposits of amyloid. Variation in section thickness markedly affected the degree of potassium permanganate oxidation.