Mounier-Kühn syndrome

Mounier-Kühn syndrome, also known as tracheobronchomegaly, is a rare condition characterized by marked dilation of the trachea and main bronchi, often associated with recurrent lower respiratory tract infections. The disorder was first described by Mounier-Kühn in 1932 and involves atrophy or absence of the elastic fibers and smooth muscle cells in the tracheal and bronchial walls. This structural weakness leads to abnormal widening of the central airways, with the tracheal diameter typically exceeding 3 cm in adults (measured on imaging). Diverticula (outpouchings) may form between the cartilaginous rings of the trachea, known as tracheoceles, which can trap secretions and promote chronic infection. The condition primarily affects the respiratory system. Patients commonly present with chronic productive cough, recurrent pneumonia, bronchiectasis, and difficulty clearing airway secretions. Some patients may experience hemoptysis (coughing up blood) and progressive dyspnea (shortness of breath). The dilated, floppy airways can collapse during expiration, contributing to airflow obstruction. The disease predominantly affects males and is most often diagnosed in adulthood, typically between the third and sixth decades of life. Some cases are associated with connective tissue disorders such as Ehlers-Danlos syndrome or cutis laxa, though most cases appear to occur sporadically without a clear genetic cause. There is no cure for Mounier-Kühn syndrome, and treatment is primarily supportive. Management focuses on aggressive airway clearance techniques, including chest physiotherapy and mucolytic agents, to reduce mucus retention and prevent recurrent infections. Prompt antibiotic treatment of respiratory infections is essential. In some cases, continuous positive airway pressure (CPAP) or tracheobronchial stenting may be used to maintain airway patency. Surgical interventions such as tracheoplasty have been reported in severe cases. Lung transplantation may be considered in patients with end-stage respiratory failure. Regular monitoring with pulmonary function tests and imaging is recommended to track disease progression.

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