Correct!
5. Tracheobronchomegaly
High attenuation bronchial impaction, often in the setting of central bronchiectasis, is very suggestive of allergic bronchopulmonary mycosis, but all the dilated bronchi in this case are clearly patent. No intrabronchial opacity or bronchial impaction is present, and no associated bronchiolitis is seen. Central bronchiectasis is frequently suggestive of allergic bronchopulmonary mycosis, whereas lower lobe predominant bronchiectasis is often seen with post-infectious etiologies. Bronchiectasis often favors the upper lobes in patients with cystic fibrosis, whereas middle lobe and lingua-predominant bronchiectasis is common with non-tuberculous mycobacterial infection and possibly even ciliary dyskinesia syndromes. The dilated bronchi in this patient are diffusely distributed throughout the upper, mid, and lower lungs; no particular zonal predilection is present. Numerous “low” air-fluid levels may be seen in various cases of bronchiectasis and may be useful for distinguishing bronchiectasis from other cystic pulmonary disorders, but this finding is not useful for distinguishing among the various causes of bronchiectasis. Fibrotic lung disease may produce traction bronchiectasis, but fibrotic abnormalities are lacking in this patient. However, the trachea and bilateral mainstem bronchi are abnormally enlarged, suggesting the diagnosis of tracheobronchomegaly, or Mounier-Kuhn syndrome.
Diagnosis: Mounier-Kuhn syndrome (congenital tracheobronchomegaly)
Discussion
Congenital tracheobronchomegaly, or Mounier-Kuhn syndrome, is a rare disorder resulting from atrophy or even absence of elastic fibers and smooth muscle tissue within the airways, resulting in dilation of the trachea and proximal bronchi. Patients typically present in childhood or young adulthood, often with recurrent respiratory tract infections, although the present may vary from severe symptoms to asymptomatic detection, and the age range of presentation is wide. Eventually excessive airway collapsibility and severe airflow obstruction may result. Bronchiectasis is common, multiple airway diverticulae may be present, and emphysema may coexist. The diagnosis may be suggested at chest radiography in adult women when the tracheal transverse and sagittal diameters exceed 21 mm and 23 mm, respectively, and when the mainstem bronchial transverse diameters exceed 19.8 mm and 17.4 mm, respectively. In adult men tracheobronchomegaly may be diagnosed when the transverse and sagittal diameters of the trachea exceed 25 mm and 27 mm, respectively, and when the transverse diameters of the right and left main bronchi exceed 21.1 mm and 18.4 mm, respectively. At CT, adult tracheal, right mainstem, and left mainstem bronchial diameters exceeding 3 cm, 2.4 cm, and / or 2.3 cm, respectively, establish the diagnosis of tracheobronchomegaly. For simplicity, these numerical values are often used at radiography, although CT is preferred for diagnosis because the airway dimensions may be measured far more accurately than with radiography. The diagnosis of tracheobronchomegaly may also be made at bronchoscopy.
Tracheobronchomegaly may also be encountered in the setting of fibrotic lung disease, but the mechanism in this circumstance is traction bronchiectasis, not an intrinsic tracheobronchial abnormality. Tracheobronchomegaly may also be seen in patients with connective tissue disorders, such as Ehlers-Danlos syndrome or children with cutis laxa.
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