LAUSR

Somatic mutations in JAK2 are associated with chronic myeloproliferative neoplasms (MPNs), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis (PMF). The most common variant, Val617Phe (JAK2), accounts for >95% of polycythemia vera and 50%–60% of essential thrombocythemia and PMF cases. Chorea is a well-described neurological complication of polycythemia vera, encompassing acute-onset occasionally reversible hemichorea and slowly progressive generalized chorea with prominent oromandibular involvement. The former usually has a vascular etiology, secondary to thrombosis, hemorrhage, or hyperviscosity, whereas the latter has a poorly elucidated pathophysiology. Here, we describe a case of late-onset generalized chorea with prominent oromandibular involvement associated with JAK2-positive essential thrombocythemia (rather than polycythemia vera) and speculate on its pathophysiology.