Anti-Ri Paraneoplastic Neurologic Syndrome in a Patient With Untreated Breast Cancer.

Paraneoplastic syndromes (PNS) refer to a broad range of disorders that can impact any part of the nervous system and are frequently immune-mediated. Although classically associated with solid tumor malignancies, PNS remain a rare phenomenon. Anti-Ri-positive (antineuronal nuclear antibody type 2-positive) PNS is highly associated with breast cancer and results in a variety of clinical presentations, including cerebellar degeneration and opsoclonus-myoclonus syndrome. In this report, we describe a case of anti-Ri-positive PNS identified in a patient with a several-year history of untreated localized breast malignancy.