Chorea in polycythemia vera: a rare presentation of hyperviscosity.

A 65-year-old woman developed severe chorea as the presenting symptom of the hyperviscosity syndrome together with polycythemia vera and an ovarian cyst. Whole blood viscosity was 69.5 centipoise at a shear rate of 1.1 s-1 (normal 12.0-22.0 centipoise). After four phlebotomies the chorea subsided completely, and the blood viscosity became normal. Hemoglobin level was stable at normal range and then increased to 18.0 g/dl with recurrence of the faciobuccal dyskinesia that disappeared promptly following the phlebotomies. This case emphasizes that in elderly patients with neurological disorders, such as chorea, polycythemia should be strongly considered as one of the treatable causes.