Paraneoplastic cerebellar degeneration mimicking development of secondary progressive multiple sclerosis in a patient with relapsing-remitting multiple sclerosis.

Paraneoplastic cerebellar degeneration (PCD) is a rare non-metastatic complication of cancer mediated by T lymphocytes and auto-antibodies directed against Purkinje cells of the cerebellum. We report a patient with relapsing-remitting multiple sclerosis who developed a progressive cerebellar syndrome with dysarthria, ataxic gait and vertigo mimicking development of secondary progressive multiple sclerosis but caused by anti-Yo antibody positive PCD associated with ovarian cancer, presenting an unusual diagnostic challenge.