Mounier-Kuhn syndrome (MKS) is a rare entitycharacterised by an enlargedtrachea and main bronchi.Despite the century-long delaybetween the first description in 1932, itisstillunder-diagnosedwithonly 300 cases reported in the literature. Histologicallyitischaracterised by an atrophy of the smooth muscle and elastic fibres of the tracheobronchialtreeresulting in impairedmucociliary clearance. The respiratorysymptoms of MKS are non-specific and appear as a recurrentrespiratory infection. Chest CT remains the gold standard for diagnosistreatmentis non-specific and based on the control of associatedrespiratorydiseases, physiotherapy and sometimessurgery. We report here the case of a 61-year-old man with a history of chronicbronchitis and recurrentpneumonitiswhowasadmitted for acute dyspnea and in whom the diagnosis of MKSwasretained. A betterknowledge of the pathologywillallow an earlydiagnosis and prevention of complications. This case illustrates the latediagnosis and management.