Unveiling Mounier–Kuhn syndrome: clinical phenotypes, imaging challenges, AI applications, and review of literature

Abstract The Mounier–Kuhn syndrome (MKS) is a rare chronic respiratory disease, first described in 1932 by Pierre-Louis Mounier–Kuhn, of unknown etiology. It is characterized by marked dilation of the trachea and main bronchi. Anatomically, MKS is classified into three types: type 1 with tracheal and bronchial dilation; type 2 with tracheal dilation accompanied by diverticula with normal bronchial diameters; and type 3 with extensive involvement of distal bronchi with both diverticula and dilation. It may present with common symptoms such as chronic cough, purulent sputum, recurrent infections, and dyspnea, or less common symptoms such as hoarseness, pneumothorax, dry cough, and sleep-disordered breathing. The diagnosis of MKS is made through a combination of patient history, respiratory function tests (possible obstructive or mixed obstructive-restrictive ventilatory defect with diffusion capacity (DLCO) reduction or normal), radiological imaging demonstrating tracheal and bronchial dilatation (≥ 30 mm for the trachea, ≥ 20 mm for the right main bronchus, and ≥ 18 mm for the left main bronchus), bronchoscopy, and the exclusion of conditions associated with tracheomalacia, both autoimmune and syndromic in origin including Ehlers–Danlos syndrome, Marfan syndrome, cystic fibrosis, and cutis laxa. In this article, we will describe two cases of MKS and provide a systematic review of the literature, emphasizing the need for multidisciplinary collaboration in the diagnosis and management of MKS and the importance of emerging technologies, including artificial intelligence-based imaging, which show promise in improving diagnostic and monitoring capabilities for this rare disorder.