Spontaneous Pneumomediastinum in a Patient With Undiagnosed Ankylosing Spondylitis.

Spontaneous pneumomediastinum (SPM) is an uncommon condition characterized by air in the interstices of the mediastinum. Management generally involves supportive care; however, if a patient inspires high concentrations of oxygen, the mediastinal air will be absorbed faster. A 23-year-old man who presented with acute-onset breathlessness with a history of more than a year of lower backache was diagnosed with SPM and accompanying ankylosing spondylitis (AS) by a chest CT and spinal MRI and was treated conservatively. This case is being reported for its uniqueness, as SPM with underlying AS is rare.