Acute STEMI in a young adult without conventional risk factors: a case report of JAK2-positive essential thrombocythemia.

The prevalence of acute coronary syndrome (ACS) in young adults (<40 years) is rising, with a substantial proportion attributable to non-atherosclerotic causes. One cause is essential thrombocythemia (ET), a myeloproliferative neoplasm (MPN) characterized by increased risk of thrombosis and bleeding. Recognizing ET as an aetiology of ACS is clinically important, as it alters acute and long-term management. This case highlights myocardial infarction as the presenting event of JAK2-positive ET in a young patient without traditional risk factors. A 31-year-old man with no cardiovascular risk factors developed severe chest pain while weightlifting. ECG revealed anterior ST-segment elevation, and troponin peaked above 22 500 ng/L. Point-of-care ultrasound showed apical wall motion abnormality, and suprasternal notch view revealed no intimal flap. Coronary angiography showed complete ostial left anterior descending artery occlusion, treated with intravascular ultrasound-guided drug-eluting stent placement. Persistent thrombocytosis after reperfusion and at follow-up, along with absence of other risk factors, prompted haematology consultation. Hypercoagulability testing revealed a JAK2 V617F mutation. ET was confirmed by bone marrow biopsy, and hydroxyurea was initiated alongside standard post-infarction therapy. The patient recovered left ventricular function. This case highlights the importance of considering MPNs as a potential cause of ACS in young patients without traditional cardiovascular risk factors. Management of ET-associated ACS is complex, requiring careful balance of thrombosis prevention and bleeding risk. Cytoreduction with hydroxyurea is key to secondary prevention. Current ACS guidelines do not specifically address ET-associated ACS, underscoring the need for further studies in this high-risk population.