Mounier-Kuhn Syndrome

Mounier-Kuhn syndrome, also known as tracheobronchomegaly, is a rare congenital abnormality of the trachea and main bronchi characterized by cystic dilatation of the tracheobronchial tree and recurrent respiratory infections. The characteristic demographic is middle-aged African-American men.

As the name suggests, there is enlargement of the trachea (coronal diameter > 25 mm measured 2 cm above the aortic arch) and central bronchi. There may be an undulating or corrugated appearance to the airways due to prolapse of redundant mucosa through tracheal rings. Tracheobronchial diverticula may also be seen. There may be collapse of the trachea and major airways on expiration. Recurrent infections leave behind areas of bronchiectasis.

Differential consideration include:

• Pulmonary fibrosis in the upper lobes: Retraction of the tracheobronchial walls, leading to tracheomegaly.
• Tracheobronchomalacia: Diffusely flaccid and dilated airway may simulate the appearance of the airway in Mounier-Kuhn syndrome. May lead to recurrent infections and bronchiectasis. May be primary or due to relapsing polychondritis, chronic airway inflammation or infection, chronic bronchitis, trauma (intubation) or cystic fibrosis.
• Allergic bronchopulmonary aspergillosis: May cause central bronchiectasis. Usually in patients with chronic asthma or cystic fibrosis. Look for central, round, or varicoid bronchiectasis; large mucoid impactions (finger-in-glove opacities); and fleeting peripheral air-space opacities.

See related post on tracheal stenosis.

Special thanks to Dr. Aiham Korbage for the case.

References

Marom EM, Goodman PC, McAdams HP. Diffuse abnormalities of the trachea and main bronchi. AJR Am J Roentgenol. 2001 Mar;176(3):713-7.