CANCER-ASSOCIATED RETINOPATHY - THE CAR SYNDROME

Experimental data from basic research and experience accumulated from the clinical examination of patients who lose vision through the specific form of paraneoplastic retinopathy referred to as the CAR syndrome, indicates this form of vision loss results from autoimmune reactions. However, the eyes of CAR patients characteristically show little evidence of immune-cell influx and exhibit no resemblance to the acute intraocular reactions of uveitis or that induced experimentally in laboratory animals. Nevertheless, the CAR patient betrays evidence of immunologic involvement through the elaboration of autoantibodies reactive with the 23 kDa retinal CAR antigen, located within the photoreceptors. The recent demonstration of the expression of this photoreceptor antigen by a culture of small cell carcinoma, has revealed an immunologic 'cancer connection' which may be responsible for the CAR patient's production of this unusual autoantibody response. CAR patients may therefore generate an autoimmune reaction against the 23 kDa CAR antigen in response to the stimulus of a neoplasm expressing the corresponding component as a cancer-associated antigen. The noninflammatory nature of this form of retinopathy suggests that, if autoimmune reactions are involved, they probably emanate from the humoral aspects of the immune system, possibly involving the autoantibodies which identify this syndrome. Consensus of opinion on the pathogenesis of CAR suggests that vision loss results as a cancer-evoked autoimmune reaction which may be controlled through appropriate therapeutic measures.