Case Presentation: 25-year-old male with a past medical history of von Willebrand disease, thrombocytosis presented to an outside hospital (OSH) with acute onset chest pain. An EKG there showed ST-segment elevation in anterior leads after which he was emergently taken to the cardiac catheterization laboratory. He was found to have an left anterior descending (LAD) artery thrombus along with severe left ventricular dysfunction (ejection fraction 15-20%). He underwent a drug-eluting stent to the LAD and required placement of an Impella device. Additionally, cardiac catheterization also revealed residual thrombus in the apical LAD, diagonal branch and moderate disease of the right coronary artery. The patient received therapy with aspirin, ticagrelor, unfractionated heparin, and tirofiban there. He was then transferred to our institution for further management of cardiogenic shock. He had no family history of premature coronary artery disease or sudden cardiac death. He smoked half pack of cigarettes per day, denied alcohol or drug use. Physical exam was normal except for the presence of an Impella. His white cell count was 18.9 K/uL, hemoglobin was 11 gm/dL, platelet count was 1238 K/uL. His basic metabolic panel was normal. His INR was 1.2 and von Willebrand factor (vWF) activity was low (42%) and vWF antigen was normal. He previously followed with hematology as an outpatient and records showed that his JAK2 was negative. Bone marrow biopsy with 50% cellularity and atypical megakaryocytes concerning for myeloproliferative disorder were found. At that time, MPL, CALR, and JAK2 exon 12 testing were negative. Due to lack of specimen stability, BCR-ABL and JAK2 V617F mutation testing were not performed. Prior laboratory evaluation including partial thromboplastin time (PTT) 37 seconds, factor VIII level of 48 and RCF of 27% suggestive of acquired von Willebrand disease, confirmed on repeat testing. His platelet count 2 years prior to this event was normal. Hematology was consulted and they recommended platelet apheresis which decreased the platelet count to 510 K/uL. He was being treated with dual antiplatelet therapy (DAPT), heparin drip at that time. A repeat echocardiogram showed an ejection fraction of 45% on Impella. He was started on lisinopril and metoprolol for goal-directed medical therapy of his acute systolic heart failure. His Impella was eventually removed in the operating room by vascular surgery. The VWF activity and antigen level were repeated after apheresis and they were normal. His platelet count continued to uptrend during the hospital stay to <1 million and he was started on hydroxyurea 1000 mg daily. He was discharged with DAPT and hydroxyurea. BCR-ABL/JAK2 V617F mutation from peripheral blood was performed-they were both negative and his bone marrow testing was deferred to a later date. Per hematology, he has a triple-negative myeloproliferative disorder consistent with essential thrombocytosis (ET), which accounts for 10-15% of ET.
Discussion: Arterial thrombosis from ET is a rare occurrence especially in the setting of negative MPL, CALR, and JAK2 exon 12 testing. Very few cases of ET with platelet counts >1 million have been studied in literature. High platelet count in the setting of a triple-negative ET in a young male without risk factors can potentially lead to a STEMI and this case is a reminds us to aggressively control risk factors.
Conclusions: Arterial thrombosis in ET is a potential consequence and should be aggressively treated to prevent fatal complications.