Late-onset Chorea with a Rare but Identifiable Cause.

Chorea is a very commonly encountered movement disorder; it has various etiologies, and it can have autoimmune, vascular, degenerative, or paraneoplastic etiology. Our patient had acute onset chorea and a strong history of smoking, which made us suspect first vascular followed by paraneoplastic cause. After ruling out common vascular and metabolic causes, his whole body positron emission tomography (PET) scan revealed a mass in the right upper lobe, a biopsy revealed a small cell carcinoma lung and a paraneoplastic panel showed antibodies positive for collapsin response mediator protein 5 antigen (CRMP-5/CV2); the patient was started on immunomodulation, chemotherapy with the variable response, he succumbed to a cardiac event after treatment.