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 (SUVmax 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.