male with recurrent pulmonary lung infections receives a computed tomography
angiography (CTA) for follow up of a known aortic dissection (not the diagnosis
in this case).
and axial CT images in lung windows are provided. There is diffuse enlargement
of the trachea and the main bronchi with a corrugated appearance of the
trachea. The axial CT image at the level of the lung apices demonstrates
enlargement of the trachea with a small right-sided tracheal diverticulum
arising posteriorly. The lung bases demonstrate cylindrical bronchiectasis.
Mounier-Kuhn syndrome, also known as congenital tracheobronchomegaly,
is a rare congenital disorder of unknown etiology. Due to associations with
Ehlers-Danlos syndrome, Marfan syndrome, and cutis laxa, it is thought to be
related to a connective tissue disorder. Pathologically, the disorder is
characterized by atrophy or absence of elastic fibers and thinning of the
muscular mucosa of the trachea and main bronchi. The trachea and main bronchi
are therefore dilated with multiple mucosal outpouchings, which collect
secretions. The lack of elastic fibers also results in a flaccid trachea, which
collapses on expiration (due to increased intrathoracic pressure) and dilates
on inspiration (due to decreased intrathoracic pressure). Due to these anatomic
and physiologic abnormalities, patients are predisposed to stagnation of
secretions with an ineffective cough reflex.
Patients are usually diagnosed between the ages of 20 and 40
and present with recurrent pulmonary infections, which often date back to
childhood. Patients may also complain of dyspnea on exertion and hemoptysis.
However, some patients are asymptomatic and diagnosed incidentally.
The imaging findings of Mounier-Kuhn include dilation of the
trachea and bronchi with numerous mucosal outpouchings between the
cartilaginous rings, resulting in a corrugated appearance. Many patients also
will develop tracheal diverticula arising from the posterolateral trachea at
the junction of the posterior membrane and the anterior cartilaginous portion
of the trachea. Numerous tracheal measurements have been published with the
transverse diameter of the trachea 2 cm above the aortic arch measuring greater
than 25-30 mm in men and 21-27 mm in women. Bronchial diameter measurements of
20-24 cm on the right and 15-23 mm on the left have also been used.
Treatment is usually
conservative and consists of physiotherapy and postural drainage with
antibiotic treatment for acute infections.
- Marom EM, Goodman PC,
McAdams HP. Diffuse abnormalities of the trachea and main bronchi. AJR Am J Roentgenol. 2001;176:713-717.
- Shin, et al.
Tracheobronchomegaly (Mounier-Kuhn syndrome): CT diagnosis. AJR Am J Roentgenol. 1988;150:777-779.
- Dee PM. Chest case of the day.
Tracheobronchomegaly--the Mounier-Kuhn syndrome. AJR
Am J Roentgenol. 1996;167:235,238.