Silent Yet Severe: A Rare Case of Unprovoked Pulmonary Embolism in a Healthy Young Adult

A 22-year-old male, a nonsmoker, nonalcoholic, and university student, presented with a 10-day history of fever, dry cough, and exertional shortness of breath corresponding to NYHA Grade II. He reported no history of leg pain, recent trauma, surgical procedures, prolonged immobilization, long-distance travel, bleeding tendencies, or any known comorbid conditions. He also denied any history of substance use or addiction. On examination, his heart rate was elevated at 114 beats/min, and his blood pressure measured 100/90 mmHg. The electrocardiogram demonstrated sinus tachycardia. Chest radiography revealed bilateral pleural effusions. Cardiac biomarkers including Troponin-I and creatine kinase MB were within normal limits. However, D-dimer levels were markedly elevated (>10,000 ng/mL), and N-terminal pro-B-type natriuretic peptide was also raised (1022 pg/ml). Bilateral arterial and venous Doppler studies of the lower limbs showed no evidence of thrombosis. A computed tomography pulmonary angiogram revealed nonenhancing hypodense areas in the segmental branches of the lower lobe pulmonary arteries bilaterally, consistent with pulmonary embolism. The patient was managed with intravenous heparin during hospitalization and transitioned to oral apixaban upon discharge. He showed clinical improvement and was discharged in a stable condition.