2566 Essential Thrombocythemia and AVM-Related Gastrointestinal Bleeding: A Rare Paradoxical Phenomenon

Abstract

INTRODUCTION: Essential thrombocythemia (ET) is a myeloproliferative neoplasm characterized by excessive platelet production. It usually presents with thrombotic events. However, rarely, essential thrombocythemia may present with gastrointestinal (GI) bleeding. This phenomenon is seen paradoxically at very high platelet counts. We present a case of GI bleeding secondary to arteriovenous malformation (AVM) in a patient with platelet counts >1 million/uL. CASE DESCRIPTION/METHODS: A 74 year old male with history of hypertension, myeloproliferative disease, on hydroxyurea therapy, complicated by deep vein thrombosis requiring inferior vena cava filter placement, ischemic stroke, was admitted to inpatient rehabilitation after suffering from acute ischemic stroke 2 weeks ago. The patient was started on clopidogrel for acute stroke. He was found to have melena and gradual drop in hemoglobin (11.5 g/dL down to 6.5 g/dL). Complete blood count showed progressive rise in his platelet count (from 937 k/uL to 2.4 million/uL). Upper endoscopy revealed one small AVM in the fourth portion of the duodenum, treated successfully with hemostatic spray. Clopidogrel was switched to aspirin and hydroxyurea dose was increased for cytoreductive therapy as suggested by hematology. Subsequent colonoscopy revealed two non-bleeding AVMs in the cecum, treated with argon plasma coagulation (APC). DISCUSSION: ET is known to increase the risk of thrombotic events, including cardiovascular events, deep vein thrombosis, pulmonary embolism, retinal artery occlusion, digit ischemia and hepatic or portal vein thrombosis. However, ET also increases the risk for bleeding paradoxically with incidence rates ranging from 5-30 percent at the time of diagnosis. In GI tract, the bleeding is mostly from AVMs in ET. This phenomenon has been associated with qualitative defects and alteration in the platelets aggregation due to depletion of high-molecular weight von Willebrand factor multimers and development of an acquired von Willebrand disease. Interestingly, incidence of bleeding in ET correlates with the severity of thrombocytosis, mostly seen with extreme thrombocytosis (platelet counts >1 million/microL) [2-3]. Previous bleeding episode and use of antiplatelet drugs may further increases the risk of bleeding. Hydroxyurea is used for cytoreduction with platelet apheresis reserved for extreme cases where platelets exceed 1.5 Million/μl.