Sporadic fatal insomnia masquerading as a paraneoplastic cerebellar syndrome

Background: Sporadic fatal insomnia is a rare prion disease that has recently been recognized. \Objective: To report a unique case of sporadic fatal insomnia in a woman with progressive cerebellar deterioration who was originally thought to have a paraneoplastic cerebellar syndrome. Design: Case report describing a patient with autopsyproven sporadic fatal insomnia. Patient: A 56- year- old woman with progressive cerebellar ataxia who was found to have a retroperitoneal non- Hodgkin lymphoma. Results: Autopsy demonstrated marked degenerative changes in the thalamus, cerebellum, and inferior olivary nucleus. A mild spongiform change was present in the thalamus and cortical gray matter. Western blot analysis confirmed the presence of abnormal, proteaseresistant prion protein ( PrPSc), characteristic of sporadic fatal insomnia. Conclusions: Clinicians should be aware of this rare prion disease and should strongly consider the importance of autopsy toward the investigation of unusual neurological diseases.