Mounier-Kuhn syndrome or congenital tracheobronchomegaly is a rare clinical and radiological condition. It is characterized by a tracheal and bronchial dilation. Fewer than 100 cases have been reported in the medical literature since the original description in 1932. The first utilization of bronchoscopy for diagnosis of this condition was recorded by Lemoine only in 1949.1 The cause of this condition is not clearly understood; however, histopathologic findings of atrophy of smooth muscles and elastic tissue in the trachea and main bronchi have been observed. Tracheobronchomegaly can be associated with tracheal and bronchial diverticuli.
A 65-year-old man, a former smoker (4 packs per year), was hospitalized for a cough with mucopurulent expectoration, dyspnea with reduction in effort tolerance, weight loss of approximately 5%, and diffuse thoracic pain. He had no history of connective tissue or autoimmune diseases but had occupational exposure to grinder’s dust and high temperature fluctuations. The patient was previously diagnosed with chronic obstructive pulmonary disease (COPD), presenting with numerous exacerbations, 2 to 3 per year for a duration of 2 to 3 weeks, over the last 15 years for which he received bronchodilator treatment and antibiotics. Physical examination revealed increased anterioposterior thoracic diameter, decreased breath sounds bilaterally with prolonged expiration, and diffuse ronchi over entire pulmonary area. Laboratory findings revealed leucocytosis with granulocytosis, iron-deficiency anemia, and an elevated erythrocyte sedimentation rate. Pulmonary function testing revealed mild restrictive respiratory impairment with FEV1 of 2.56 L (86%), vital capacity (VC) of 3 L (76.3%), and FEV1/FVC of 101%. MEF 50 was 2.70 L (65.7%). Chest radiography showed prominent interstitial markings, hyperinflation with horizontal ribs, and flattening of the diaphragm (Fig. 1). Computed tomography (CT) images revealed bilateral cystic bronchiectasis, dilation of the trachea and main bronchi: maximum diameter of the trachea over 4 to 5 cm and of main bronchi over 2 to 3 cm (Fig. 2).
During bronchoscopy the tracheomegaly with transverse and anteroposterior diameters increased over 2 cm was noted. There was a sharp angle between posterior and lateral walls of the trachea. There was evidence of diverticuli involving posterior tracheal wall, tracheobronchial hypotonic dyskinesia, and flabby bronchial walls, during cough and respiration. There were changes in the tracheobronchial statics, which extended form the trachea to the main and segmental bronchi. Findings indicative of bronchiectasis with abounding mucopurulent secretions involving basilar segments was also present (Figs. A, B). Bronchial lavage sample was negative for bacteria, fungus, and acid-fast bacilli (Supplemental Digital Content 1, http://links.lww.com/LBR/A109).
For a better visualization of the entire tracheobronchial architecture, we performed a bronchography with Ultravist (Fig. 3), which showed tracheomegaly, tracheal diverticula, and cystic bronchiectasis in right inferior lobe bronchus and middle lobe bronchus with irregularities of bronchial contour, image of chronic bronchitis, and cystic bronchiectasis involving right lower lobe and middle lobe bronchi.
On the basis of these findings, the patient was diagnosed with Mounier-Kuhn syndrome and was discharged from the hospital after 7 days of treatment with oral levofloxacin (750 mg daily), mucolytics and postural drainage including aerosols with acetylcysteine and bronchodilators.
The Mounier-Kuhn syndrome is a congenital condition characterized by a distinct tracheobronchial dilatation due to the muscular and elastic tissue atrophy in trachea and in the bronchial walls, which presents more frequently in males, and it is usually diagnosed in the third and fourth life decade. The clinical presentation significantly varies from minimal symptoms, wherein the pulmonary function is maintained, to severe respiratory insufficiency and death. Different airway regions are affected, starting from trachea and up to the fourth bronchial generation. Although its cause is not entirely known, tracheobronchomegaly is related to the family susceptibility and possible autosomal recessive inheritance. More often, the cases are sporadic.2
The Mounier-Kuhn syndrome has 3 subtypes. In type 1, there is a slight symmetric dilation in the trachea and main bronchi. In type 2, the dilation and diverticuli are distinct. In type 3, diverticular and saccular structures extend to the distal bronchi. The main problems associated with this disease are ineffectual cough resulting from pathologic dilation of the tracheobronchial tree and the impairment of mucociliary apparatus activity. These lead to difficulties in expectorating secretions and recurrent lower respiratory tract infections.3 Symptoms are nonspecific. In the absence of infection, this disease process can be asymptomatic. Bronchiectasis and lower respiratory tract infections are clinically prominent; thus, the recurrent pneumonias and fibrosis can eventually occur.3–5 In the aforesaid case, the productive cough was predominant and taking into consideration the fact that the patient was a smoker and worked in a noxious environment, the symptoms were attributed to COPD and bronchiectasis.
The diagnosis is often made by CT scans, which shows abnormally large airways. In adults, the diagnostic criteria are: diameters of the trachea >30 mm; of the right main bronchus >20 mm; and of the left main bronchus >18 mm.5–7
On pulmonary function testing, decreased flow, increased tidal volume, and dead space can be observed.8 Bronchoscopy can detect the pathologic processes that affect the tracheobronchial structures—especially, the dilation in trachea and main bronchi during inspiration and even their collapse during expiration and coughing.
In this case, the diagnosis was delayed, the patient being treated for several years as a case of COPD. The frequency of the infectious exacerbations during the year before admission motivated the decision to perform a bronchoscopy, an investigation that settled the final diagnosis and changed the therapeutic approach of the case.
The recurrent respiratory infections with no therapeutic response were likely explained by the anatomic modifications from airway collapse with the retention of the secretions and by the existence of cystic bronchiectasis seen on bronchography.
Differential diagnosis is also considered in relation to other connective tissue diseases, the ataxia-telangiectasia, ankylosing spondylitis, Ehlers-Danlos syndrome, Marfan syndrome, Kenny-Caffey syndrome, Brachmann-de Lange syndrome, and cutis laxa (elastolysis), which are also associated with secondary tracheobronchial enlargement. In addition, sarcoidosis, diffuse interstitial pneumonia, and cystic fibrosis may determine secondary tracheomegaly due to fibrotic tractions during their evolution.8,9
Asymptomatic patients require no specific treatment. Smoking cessation is highly beneficial, as is the minimization of exposure to industrial and occupational irritants and pollutants. In symptomatic patients the therapy is supportive, limited to respiratory physiotherapy for eliminating secretions and antibiotic use during infectious exacerbations. Although tracheal stenting has been helpful in the severe cases, this intervention is rarely performed because of the diffuse nature of the disease and inability to clear secretions as well as long-term complications from the airway stents. Lung transplantation provided no confirmed benefit concerning the risk of morbidity and death.10
The particularities of this case consist in the delayed diagnosis. This patient was previously diagnosed with COPD and diffused interstitial lung disease due to occupational environment and was accordingly treated with no satisfactory response to repeated treatments. In addition, there was discordance between marked exertional dyspnea and the pulmonary function tests, which were just slightly altered. The bronchoscopy and CT scanswere performed late in the course of his disease but eventually established the diagnosis of tracheobronchomegaly.
In conclusion, the bronchoscopic examination is relevant in selected patients with COPD with refractory symptoms to treatment. This case highlights the importance of recognizing central airway disorders as imitators COPD.
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7. Jaiswal AK, Munjal S, Singla R, et al..A 46-year-old man with tracheomegaly, tracheal diverticulosis, and bronchiectasis: Mounier-Kuhn syndrome.Lung India.2012;29:176–178.
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9. Noori F, Abduljawad S, Suffin DM, et al..Mounier-Kuhn syndrome: a case report.Lung.2010;188:353–354.
10. Menon B, Aggarwal B, Iqbal A.Mounier-Kuhn syndrome: report of 8 cases of tracheobronchomegaly with associated complications.South Med J.2008;101:83–87.
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