Obese Adolescent with Factor V Leiden-Related Pulmonary Embolism: Case-Based Insight into Paediatric Thrombosis Management

Background/Objectives: Paediatric pulmonary embolism (PE) is rare but potentially lethal, and its diagnosis is complicated by non-specific presentations and multiple predisposing risk factors. We describe a 15-year-old girl who presented with features of pulmonary hypertension and was found to have extensive pulmonary embolism with right heart strain. Methods: The diagnosis was established with echocardiography, computed tomography pulmonary angiography (CTPA), and Doppler ultrasonography. Results: Her predisposing risk factors comprised obesity (BMI 33 kg/m²), a family history of thrombosis, and heterozygous Factor V Leiden. In retrospect, a six-week illness treated as bronchitis, with haemoptysis and exertional syncope, was the probable index embolic event; the markedly elevated right-sided pressures tolerated without haemodynamic collapse indicate a right ventricle that had adapted over that interval. Anticoagulation with low-molecular-weight heparin, titrated to anti-factor Xa activity, was followed by a vitamin K antagonist while antiphospholipid syndrome was excluded and then by rivaroxaban, with clinical, biochemical, and radiographic improvement. Conclusions: This report underscores the need for greater awareness of PE in children, the value of revisiting a recent respiratory illness as a possible index embolic event, and the evolving role of direct oral anticoagulants in its management.