Persistent hypoxia with mosaic attenuation despite negative CT pulmonary angiography in chronic thromboembolic...

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare but serious complication of acute pulmonary embolism. It may be clinically silent and often presents with non-specific symptoms, making diagnosis challenging. We present the case of a man in his 40s who presented with shortness of breath and acute hypoxic respiratory failure. His hypoxia persisted despite pneumonia and superimposed human metapneumovirus infection treatment.Despite two negative CT pulmonary angiograms, clinical suspicion for pulmonary vascular disease remained high given the otherwise unrevealing diagnostic workup, persistent tachycardia, right ventricular dysfunction on echocardiography and persistent mosaic attenuation on CT of the chest. A ventilation-perfusion scan ultimately showed CTEPH, later confirmed by right heart catheterisation and pulmonary angiography.This case highlights the complex presentation and diagnostic challenges of CTEPH. It emphasises that CTEPH should remain on the differential in patients with persistent hypoxia and signs of pulmonary hypertension, even when CT imaging does not demonstrate pulmonary embolism.