Mounier-Kuhn syndrome

Clinical History

A 42-year-old male patient presented to outpatients respiratory clinic with a long standing history of cough productive of sputum and regular chest infections.

Imaging Findings

The initial chest radiograph revealed multiple intrapulmonary cavities, a dilated trachea and a well defined right hilar opacity (Figure 1). The right lateral chest radiograph detected an area of airspace shadowing at the right lung base (Figure 2). In view of the hilar mass, a conventional CT chest was requested rather than an HRCT. However, the hilar shadow turned out to be one of the dilated bronchi which was filled with fluid. Axial CT images confirmed the presence of a dilated trachea which also contained posterior tracheoceles made up of prolapsed mucosa (Figure 3). Multiple sacculations, all connected to the bronchial tree could be seen, some of which contained an air/fluid level (Figure 4, 5). The coronal reformatted images shows absence of the cavities at the lung periphery (Figure 6). Follow-up chest radiograph taken 17 months post diagnosis revealed an increase in both the size and number of the cavities.

Discussion

Tracheobronchomegaly was first described by Mounier-Kuhn in 1932. The syndrome's characteristics include dilatation of the trachea and bronchi together with recurrent chest infections. Its cause is unknown but a decrease in the amount of elastic and muscle fibres has been reported. Mounier-Kuhn itself is a congenital disease however tracheobronchomegaly may also occur as a result of Ehlers-Danlos syndromes, severe upper lobe fibrosis as in sarcoidosis and cystic fibrosis and in chronic airway inflammation as in allergic bronchopulmonary aspergillosis. The disease is commoner in males and usually diagnosed in the 40 - 50 year age group. [1, 2]
The clinical presentation is nonspecific with symptoms overlapping those of chronic bronchitis and bronchiectasis. Some patients are asymptomatic having been diagnosed incidentally. Most patients present with a chronic cough, recurrent chest infections, haemoptysis and shortness of breath. An increase in the dead space and tidal volume is seen on pulmonary function tests. [3]
Tracheobronchomegaly is subdivided into three. Type 1 is subtle diffuse enlargement of the trachea and major bronchi, while type 2 is more obvious bizarre enlargement which may include sacculations in the major bronchi. In type 3, the diverticula and sacculations extend into the distal bronchi. [3]
The widened and corrugated trachea can usually be diagnosed on plain radiography, however, this can be missed if it is not specifically looked for. Specific measurements for diagnosis have been set. Tracheobronchomegaly is confirmed once the trachea exceeds 3cm in diameter, the right main bronchus exceeds 2.4cm while the left main exceeds 2.3cm. HRCT confirms the dilatation and allows more accurate measurements. The dilatation and sacculation of distal bronchi can also be appreciated. [2]
No treatment is advocated in asymptomatic patients while smoking cessation is actively encouraged. Intense broad spectrum antibiotics are administered in acute infection and postural physiotherapy for drainage is advised. Surgery has minimal role in treatment. [2]
Mounier-Kuhn syndrome is a diagnosis to consider in patients presenting with chronic cough, recurrent infections and sputum production. The tracheal diameter should be included as one of the review areas when interpreting a plain chest radiograph.

Differential Diagnosis List

Final Diagnosis

Mounier-Kuhn Syndrome (tracheobronchomegaly)

URL:	https://www.eurorad.org/case/10176
DOI:	10.1594/EURORAD/CASE.10176
ISSN:	1563-4086