Unilateral Pulmonary Artery Lesion in an Immunocompromised Patient

We report a 62-year-old man with myelodysplastic syndrome on immunosuppressive therapy who presented with right lung consolidation and neutropenia. Despite broad antimicrobial therapy for presumed pneumonia, negative microbiologic studies including bronchoalveolar lavage, and a nondiagnostic transbronchial biopsy, serial computed tomography (CT) scans showed progressive right-sided consolidation, pleural effusion and CT signs of pulmonary hypertension. A routine contrast-enhanced CT revealed a filling defect in the right pulmonary artery (PA). Dedicated CT pulmonary angiography confirmed persistent unilateral PA obstruction; together with pulmonary hypertension and a lack of improvement despite anticoagulation, this raised concern for chronic thromboembolic disease and PA malignancy. Fluorodeoxyglucose positron emission tomography (FDG PET) CT demonstrated mildly heterogeneous FDG uptake (SUV_max 2.9) favouring thrombus, and endobronchial ultrasound-guided transbronchial needle aspiration yielded necrotic thrombotic material. Pulmonary endarterectomy, performed after interval clinical worsening, confirmed a chronic organizing septic thrombus. Weeks later, haemorrhagic infarction caused massive haemoptysis requiring wedge resection of the lung. This case highlights a rare septic thrombus in a unilateral PA leading to pulmonary infarction in an immunocompromised host.