[A case of paraneoplastic retinopathy with serum antibody against retinal soluble 70 kDa protein]

We report a case of paraneoplastic retinopathy in a patient who was found to have small cell carcinoma of the lung and was shown to have serum antibody against retinal soluble 70 kDa protein. A 71-year-old woman visited her ophthalmologist for gradual visual loss in both eyes. Although she underwent uncomplicated cataract surgery in her left eye, she was referred to our hospital because of progressive visual deterioration in November 1994. On admission, her corrected visual acuity was 0.3 OD and hand motion OS. Funduscopic examination showed narrowing retinal arteries, pigment epithelial mottling in the posterior retina bilaterally, and optic disc pallor in the left eye. An electroretinogram demonstrated marked reduction in the a and b waves. Bilateral central scotomas were detected by kinetic perimetry. We pursued further examination for systemic disease, and identified increased serum level of neuron specific enolase and radiographically abnormal shadow in the chest. Transcutaneous needle biopsy of the mediastinum confirmed small cell carcinoma. In western blot analysis the patient's serum reacted strongly with soluble retinal proteins of 70 kDa molecular weight, although the 26 kDa CAR antigen was not labeled. This patient was diagnosed as having paraneoplastic retinopathy due to small cell carcinoma and unusual serum protein which responded to an antigen with a molecular weight of 70 kilodaltons.