Mounier-Kuhn syndrome incidentally diagnosed during the evaluation of atypical chest pain: CT findings and diagnostic challenges.

Mounier-Kuhn syndrome, or tracheobronchomegaly, is a rare disorder characterized by abnormal enlargement of the trachea and main bronchi. It may remain clinically silent or present with recurrent respiratory infections and chronic respiratory symptoms. We report the case of a 60-year-old non-smoking man who presented with intermittent atypical chest pain without respiratory symptoms or a history of recurrent pulmonary infections. Electrocardiography, echocardiography, and repeated cardiac troponin measurements were normal, and no specific cause of the chest pain was identified. Contrast-enhanced thoracoabdominopelvic computed tomography revealed marked tracheal enlargement, measuring 34 mm in the transverse diameter and 31 mm in the anteroposterior diameter on axial images, associated with tracheal diverticula and enlargement of the right main bronchus (22 mm), whereas the left main bronchus measured 17 mm. Bilateral centrilobular emphysematous changes and a few calcified lymph nodes were also observed, without bronchiectasis or active pulmonary infection. Pulmonary function testing was reported as normal, although detailed spirometric values were unavailable for retrospective review. These findings supported an incidental diagnosis of Mounier-Kuhn syndrome, with no evidence of a causal relationship between the syndrome and the presenting chest pain. This case highlights the importance of recognizing marked tracheal enlargement and characteristic diverticula on CT, even in patients without respiratory symptoms. In asymptomatic patients with preserved pulmonary function and no significant airway complications, management should be individualized, while the clinical significance of associated emphysematous changes and the optimal strategy for long-term surveillance remain uncertain.