High-titer collapsin response-mediating protein-associated (CRM-5) paraneoplastic optic neuropathy and vitritis as the only clinical manifestations in a patient with small cell lung carcinoma

Paraneoplastic optic neuropathy (PON) is a rare syndrome usually associated with small cell lung carcinoma. In the 27 rigorously reported cases, neurologic manifestations other than visual loss have been present in all but 2. In the single case in which vision improved in response to treatment of the cancer, the collapsin response-mediating protein (CRMP)-5 titer did not change, and the ophthalmic examination was not detailed. We describe a patient with optic neuropathy and vitritis as the only clinical manifestations of PON marked by an extremely high titer of CRMP-5 antibody. Treatment of the underlying small cell lung cancer coincided with resolution of the visual abnormalities and a dramatic decrease in the CRMP-5 titer.