We present the case of a 54-year old woman referred to our service with an unusual presentation of an under-diagnosed condition. A life-long non-smoker, she was referred to respiratory services by our emergency department with a left sided pneumothorax, progressive dyspnoea on exertion, and recurrent chest infections. Subsequent investigation yielded findings consistent with Mounier-Kuhn syndrome (Tracheobronchomegaly), a condition characterised by marked dilatation of the proximal airways, recurrent chest infection, and consequent emphysema and bronchiectasis. Although rarely diagnosed, some degree of Mounier-Kuhn syndrome may occur in up to 1 in 500 adults.