Mounier-Kuhn Syndrome Flare With Pleuritic Chest Pain: A Discussion of Complications and Management.

Background: Mounier-Kuhn syndrome (MKS), or tracheobronchomegaly, is a rare disorder characterized by dilation of the trachea and main bronchi due to atrophy of elastic and smooth muscle fibers. It is associated with recurrent respiratory infections, bronchiectasis, and airway collapse. Although radiological diagnosis is well established, clinical recognition remains delayed in many cases due to the disease's rarity and nonspecific presentation. Case Presentation: We present a 56-year-old male with a known history of MKS who presented with pleuritic chest pain, productive cough, and constitutional symptoms. Computed tomography (CT) scans of the chest showed significant tracheobronchomegaly with posterior tracheal diverticulum and cystic bronchiectasis. Laboratory evaluation was unremarkable, and infectious and autoimmune workups were negative. The patient was treated conservatively with pulmonary hygiene, bronchodilators, and symptom-targeted therapy, leading to gradual improvement. Discussion: This case dives into a noninfectious symptomatic flare of MKS, expanding the clinical understanding of its complications. We explore the pathophysiology of pleuritic pain in this setting and review diagnostic delays, bronchiectasis-related morbidity, and therapeutic strategies. Advances in interventional pulmonology, including airway stenting and tracheobronchoplasty, offer promising outcomes in selected patients. Early identification, structured imaging assessment, and a multidisciplinary approach are key in managing this complex syndrome.