RESUMO
ST-segment elevation myocardial infarction (STEMI) in young adults is a rare occurrence that requires a thorough investigation to determine the underlying cause. Herein, a young female patient presented with dull retrosternal chest pain associated with nausea and left arm numbness. Cardiac-specific troponin was elevated and the electrocardiogram revealed ST-segment elevation in the inferior wall leads indicative of myocardial infarction. The patient was started on dual antiplatelet therapy (DAPT) and emergency coronary angiography was performed, revealing a 20% stenosis in the left circumflex artery and evidence of a thrombotic lesion in the posterolateral branch (PLB), which was deemed unsuitable for intervention. During the diagnostic workup, the patient tested positive for antinuclear antibodies and was ultimately diagnosed with systemic lupus erythematosus (SLE) and antiphospholipid syndrome. This case highlights the rarity of STEMI as an initial presentation of SLE. It emphasizes the importance of considering autoimmune disorders in young patients with acute myocardial infarction and the need for a comprehensive evaluation and appropriate management in such cases.