Anti-Ri-Antibody-Associated Paraneoplastic Syndrome in a Man with Breast Cancer Showing a Reversible Pontine Lesion on MRI

BACKGROUND: Paraneoplastic neurological disorders associated with anti-Ri-antibodies, which are typically present with opsoclonus-myoclonus-ataxia. Most cases with anti-Ri-antibodyassociated paraneoplastic syndrome due to breast cancer occur in women - its occurrence in men is extremely rare. CASE REPORT: We present herein the case of a male patient with breast cancer who had atypical anti-Ri-antibody-associated paraneoplastic syndrome presenting as complete horizontal ophthalmoplegia, left trigeminal sensory symptoms, and truncal ataxia. Following the diagnosis of paraneoplastic syndrome, chemotherapy and immunomodulating treatment including intravenous immunoglobulin and oral prednisolone were administered. Although the patient was negative for serum anti-Ri-antibodies 14 weeks later, his symptoms persisted. CONCLUSIONS: To our knowledge, this is the first case report of ophthalmoplegia without opsoclonus-myoclonus in a male anti-Ri-antibody-positive patient with breast cancer.

Paraneoplastic Syndrome

Paraneoplastic syndrome is a rare neurologic disorder caused not by the direct invasion or metastasis of cancer, but by the remote effects of cancer. The central- and peripheral-nervous system or neuromuscular junction area were involved in this syndrome. The pathogenesis was thought as the autoimmune disease, the result of an immunologic response to cancer and to cross-react with self-cells of the nervous system or of the neuromuscular junction, causing neuronal dam-age. Specific forms of this syndrome are often associated with specific paraneoplastic autoantibodies and cancer. The onset of neurological symptoms and detection of these antibodies often precede the diagnosis of the cancer; therefore, detection of these antibodies greatly assists the diagnosis of this syndrome and prompts investigations for the underly-ing cancer. Some paraneoplastic central neurological syndromes, such as cerebellar degeneration, limbic encephalitis, and necrotizing myelitis, were not improved by putative pathogenic autoantibodies, or by immunosuppresant or tumor removal, inspite of improvement in other peripheral neurologic syndrome, Lambert-Eaton myasthenic syndrome, neu-romyotonia, and Stiff-man syndrome. A more detailed understanding of the relationship between the cancer and the neural involvement from the molecular biological standpoint may lead to rational tumor therapy and elucidation of the mechanism of neural death. Here, major clinical forms with well-known antineuronal antibodies and specific cancers are reviewed.