Disproportionate respiratory deterioration in severe Mycoplasma pneumoniae pneumonia caused by airway obstruction and thromboembolism: a case report

Mycoplasma pneumoniae (MP) infection is typically mild in children; however, dysregulated immune responses may lead to severe pulmonary and vascular complications.We report a previously healthy 9-year-old boy who developed an unusual combination of massive pleural effusion, plastic bronchitis-like mucus plugging, pulmonary thromboembolism, and intracardiac thrombus during MP pneumonia.Despite initial therapy, he experienced recurrent unilateral lung collapse accompanied by abrupt hypoxemia.Computed tomography demonstrated complete left-lung collapse with embolism in the right pulmonary artery, and echocardiography revealed a mobile thrombus within the right ventricle.Bronchoscopic removal of an obstructing mucus cast resulted in rapid re-expansion of the lung.Anticoagulation with unfractionated heparin followed by apixaban led to complete resolution of both pulmonary and intracardiac thrombi.This case highlights the broad immunologic spectrum of severe MP infection and emphasizes the importance of considering airway obstruction and thromboembolic complications when clinical deterioration appears disproportionate to radiographic findings.Early bronchoscopy, appropriate imaging, and prompt anticoagulation are essential for optimal outcomes.