Tracheobronchomegaly—the Mounier-Kuhn syndrome

Tracheobronchomegaly (TBM) is a rare disorder of the lower respiratory tract characterised by marked dilatation of the trachea and the central bronchi associated with recurrent lower respiratory tract infections. The condition was first identified as a distinct clinicopathological entity by Mounier-Kuhn in 1932 and has been frequently referred to as the Mounier-Kuhn syndrome. The most usual alternative designation, tracheobronchomegaly, was introduced by Katz et al (1962) in a definitive review of the condition. The condition is frequently overlooked on the basis of the chest radiographs alone, although specific diagnostic features exist, as will be described. The bronchogram provides a very characteristic picture in this condition well demonstrated in the two cases under review. A little emphasised feature of the bronchograms is an abrupt transition to normal calibre of the terminal airways. A 52-year-old white woman had had recurrent bouts of respiratory tract infections over at least two decades but with marked worsening over the previous five years, during which time she developed a chronic productive cough. There was no family history of lung disease and the patient had never smoked. The only abnormality on physical examination was the auscultation of intermittent rhonchi bilaterally. Pulmonary function tests and arterial blood gases were entirely normal. The chest radiograph revealed normal lungs apart from a thinwalled cystic lesion containing a small quantity of fluid in the right hilar region (Fig. 1).