Transient floating thrombus of the internal carotid artery associated with the JAK2V617F mutation

Essential thrombocythemia (ET) is a myeloproliferative disorder (MPD) characterized by sustained elevated platelets. Cerebrovascular disorders can be a complication of ET, with thromboses of cerebral veins occurring more frequent than those of arteries [1, 2]. We describe a 33-year-old woman with no cardiovascular risk factors who experienced an acute ischemic stroke in the left middle cerebral artery territory (MCA). The carotid duplex on admission showed a free-floating thrombus (FFT) in the left internal carotid artery (Fig. 1a, b) that was not producing flow aceleration. However, the thrombus disappeared 2 h later without any clinical deterioration, as shown by a second carotid duplex. The arteriography confirmed these results (Fig. 1c). A brain infarction in the left MCA territory was observed on MRI (Fig. 1d). Peripheral blood showed a platelet count of 505 9 10/L. Additional studies, including an extensive battery of tests for coagulopaties and a complete cardiology study, were negative. The JAK2 mutation was detected in peripheral blood samples by a multiple allelespecific PCR (MAS-PCR). The thrombocytosis decreased spontaneously, as the platelet count dropped from 487 9 10/L at 3 months to 452 9 10/L after 6 months. Bone marrow aspiration showed clustered hyperlobulated megakaryocytes. She was diagnosed with MPD and specifically ET. Antiplatelet treatment was initiated as secondary stroke prevention. The patient presented a good outcome, with progressive neurological improvement. The presence of a mobile FFT in the internal carotid artery as cause of brain ischemia is infrequent and its prevalence and natural history are not well understood. The main associated pathologies are hypercoagulability, carotid dissections, trauma and plaque, although in many cases the association is not identified [3]. Philadelphia-negative MPD, especially ET and polycythemia vera (PV) may be associated with thrombi development, although they are produced more frequently in veins than in arteries [1, 2]. Recent diagnostic criteria for ET have lowered the platelet threshold from 600 9 10/L to 450 9 10/L [4]. Therefore, since the platelet count is not always highly elevated at the time of stroke, the diagnosis of ET is difficult. In our case, a complicated carotid thrombus was the initial presentation of an ET even in presence of mild thrombocythemia. The acquired Janus kinase 2 V617F mutation (JAK2) was recently identified in patients with MPDs [5]. This mutation has been found in more than 90% of patients with PV and in approximately 50% of those with ET, which led to a recent update of the diagnostic algorithms for MPDs, including the JAK2 mutation as a major criterion [4]. The risk of arterial thrombosis is significantly increased in patients with MPDs and the JAK2 mutation (OR 2.49, 95% CI 1.71–3.61) [1] independently of the V617F allele burden [6]. To the best of our knowledge, the presence of mobile floating thrombi in the extracranial carotid arteries associated with the presence of P. Martinez-Sanchez (&) R. Cazorla-Garcia J. Medina-Baez B. Fuentes E. Diez-Tejedor (&) Department of Neurology and Stroke Center, IdiPAZ Research Institute, La Paz University Hospital, Autonoma University of Madrid, Paseo de la Castellana 261, 28046 Madrid, Spain e-mail: patrindalo@hotmail.com