DOI: https://doi.org/10.36347/sjmcr.2026.v14i08.006

Pages: 1779-1781

Background: Atypical antipsychotics, particularly olanzapine, are widely used first-line agents for psychotic and mood disorders due to their favorable neurological side-effect profile compared to first-generation antipsychotics. However, their association with severe systemic adverse events, such as venous thromboembolism (VTE) and pulmonary embolism (PE), is an increasingly recognized but underdiagnosed risk. Case Presentation: A 30-year-old male with no prior psychiatric or medical history was admitted for schizophreniform disorder and initiated on olanzapine (10 mg/day). After five weeks of successful psychiatric stabilization, the patient acutely developed bilateral chest pain and exertional dyspnea. Electrocardiography (ECG) demonstrated sinus tachycardia and an S1Q3T3 pattern. A computed tomography pulmonary angiogram (CTPA) confirmed a right proximal pulmonary embolism. A comprehensive workup for inherited and acquired thrombophilia - including antithrombin, protein C, protein S activities, and antiphospholipid antibodies - was entirely negative. No classic immobility or lifestyle risk factors were present. Olanzapine was discontinued, and the patient was successfully cross-tapered to aripiprazole while receiving apixaban. Complete resolution of the PE was radiologically confirmed at three months. Conclusion: This case highlights the necessity of maintaining a high index of clinical suspicion for thromboembolic complications in patients treated with olanzapine, even in young individuals without baseline risk factors. Early recognition and interdisciplinary management are vital to preventing mortality.