[Myeloproliferative syndrome as a cause of chorea].

With the aim of reporting an unusual association, we present the case of a 78-year-old female, with a diagnosis of essential thrombocytemia (ET), JAK 2 positive, of more the 20 years' evolution, without evidence of acute transformation, and with the appearance of an associated neurological condition characterized by abnormal choreic movements, during the last year of the evolution of the hematological disease. On the other hand, chorea is a type of movement disorder characterized by involuntary, sudden movements, that can occur in one part of the body and then spread to others. Most cases of chorea are caused by structural or functional problems in the basal ganglia. It can be hereditary or acquired. In the literature, there are isolated reports of the association between adult-onset chorea and JAK2 mutation, especially related to polycythemia vera. The pathogenesis of chorea associated with myeloproliferative syndromes is unknown. It has been postulated that the gain of a function conferred by the JAK 2 mutation on the non-mutated gene could lead to a pro-inflammatory status in the neurons of the basal ganglia, which would alter their signaling pathways and therefore their functioning. For this reason, neurologists usually recommend ruling out the possibility of underlying myeloproliferative processes in adult patients diagnosed with acquired chorea whose etiology has not been established.