An Amino Acid with Killer Instincts: Pulmonary Embolism Secondary to Hyperhomocysteinemia

Pulmonary embolism (PE) is a life-threatening manifestation of venous thromboembolism, typically associated with identifiable risk factors such as immobilization, surgery, malignancy, or trauma. However, in young individuals without apparent triggers, underlying thrombophilic states must be investigated. Hyperhomocysteinemia is an often overlooked yet reversible metabolic risk factor contributing to thrombogenesis. We report a 31-year-old male electrician presenting with acute-onset breathlessness, pleuritic chest pain, and cough. Clinical evaluation revealed tachypnea, tachycardia, and hypoxemia. Electrocardiography demonstrated sinus tachycardia with an S1Q3T3 pattern. Arterial blood gas analysis showed hypoxemia with respiratory alkalosis. Computed tomography pulmonary angiography confirmed a significant thrombus in the right main pulmonary artery causing >50% luminal obstruction. Echocardiography revealed right heart strain. Routine thrombophilia workup was negative; however, markedly elevated serum homocysteine (>65 μmol/L) with low folate and borderline Vitamin B12 levels was noted. The patient was treated with anticoagulation and vitamin supplementation with clinical improvement. This case highlights hyperhomocysteinemia as a reversible yet under-recognized cause of unprovoked PE. Early detection and correction can significantly reduce recurrence risk and improve outcomes.