An unusual case of persisting hypoxia in a patient with a thrombolysed pulmonary embolism.

Exertional breathlessness and hypoxia are common presenting complaints in acute medicine. We describe a case where the patient continued to have persistent hypoxia even after the primary cause (pulmonary embolism) was diagnosed and treated. The hypoxia persisted as an enigma, its cause remaining elusive till diagnosed. Standard first-line investigations would not have reached the underlying diagnosis in this case and, as such, it demonstrates the keen clinical sense and complex investigative strategy required to solve the puzzle. © Royal College of Physicians 2020. All rights reserved.