Images of the month: An incidental finding of spontaneous pneumomediastinum (Hamman's syndrome) secondary to diabetic ketoacidosis during the coronavirus pandemic.

Hamman's syndrome is a spontaneous pneumomediastinum and is described as a rare complication of diabetic ketoacidosis (DKA). It typically follows a self-limiting course after successful treatment of the underlying DKA. We describe a case of a 28-year-old woman with type 1 diabetes presenting with facial pain, vomiting and abdominal pain. She also complained of dyspnoea and chest pain. She was diagnosed and treated for DKA triggered by a dental abscess. Given the presentation during the coronavirus pandemic, a computed tomography pulmonary angiography was performed in line with the diagnostic pathway for COVID-19, which incidentally showed a significant pneumomediastinum and pneumopericardium. The patient was initially investigated for oesophageal rupture secondary to vomiting (Boerhaave's syndrome), however, remained clinically stable throughout. Follow-up computed tomography showed near-complete resolution of pneumomediastinum with no intervention other than treatment of DKA. This therefore confirmed Hamman's syndrome.We propose that given the benign nature of the condition and the incidental finding in this report, as well as poor identification of mediastinal gas on chest X-ray, Hamman's syndrome is more common than reported. © Royal College of Physicians 2020. All rights reserved.