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Auricular chondritis in fawn-hooded rats. A spontaneous disorder resembling that induced by immunization with type II collagen.

A spontaneous apparently unique auricular chondritis in the pinna of fawn-hooded rats is described. The chondritis was bilateral, with adult onset, and resulted in a marked thickening of the auricular cartilage. Microscopically, islands of proliferative cartilage were present, and at the margins between the normal cartilage and the thickened abnormal cartilage a marked cellular inflammatory response was present. The condition was familial in rats of the fawn-hooded strain and appeared to be unrelated to the platelet storage pool deficiency in this strain of rats. Biochemically no increased synthesis of pinna cartilage was detected. No histopathologic lesions were detected in other cartilaginous tissues of affected rats. The lesions in the pinna bore a striking resemblance to those induced in rats by immunization with Type II collagen. The spontaneous condition described herein may, therefore, represent a unique model of relapsing polychondritis of human beings, a disease with auricular chondritis associated with antibodies to Type II collagen.