Non-ST-Elevation Myocardial Infarction as the Initial Manifestation of Calreticulin-Positive Essential Thrombocythemia: A Case Report.

Essential thrombocythemia (ET) is a rare myeloproliferative neoplasm characterized by excessive platelet production and a predisposition to thrombotic or hemorrhagic complications. We report a case of a 62-year-old male with no conventional cardiovascular risk factors who presented with a non-ST-segment elevation myocardial infarction (NSTEMI). Initial coronary angiography showed isolated proximal LAD stenosis. Laboratory tests revealed marked thrombocytosis (>1,000,000/μL) and a CALR mutation, confirming a diagnosis of ET. The patient was treated with percutaneous coronary intervention (PCI), dual antiplatelet therapy, and cytoreductive therapy with hydroxyurea, leading to a favorable outcome. This case illustrates how ET, particularly CALR-mutated subtypes, can manifest as acute coronary syndrome in the absence of atherosclerosis and underscores the need to consider hematologic malignancies in atypical presentations of myocardial infarction.