Mounier-Kuhn syndrome is a pathological expansion of the lumen of the trachea and proximal bronchi caused by structural defects in their walls. The anatomical anomaly is accompanied by a clinic of recurrent respiratory tract infections: a characteristic “vibrating” cough with purulent sputum, wheezing when breathing, constant shortness of breath, hemoptysis. The presumed diagnosis is clarified by the results of tracheobronchoscopy, radiography, bronchography, computed tomography. Supportive therapy is aimed at relieving recurrent infection: during exacerbations, antibiotic therapy, sanitization bronchoscopy, inhalation, massage are performed.
ICD 10
Q32.1 Other malformations of the trachea
Meaning
Mounier-Kuhn syndrome (tracheobronchomegaly, megatrachea, tracheobronchoectasia, tracheocele) is a congenital dilation of the tracheobronchial tree. The first mention of the anomaly – “pulsating diverticulum of the trachea” – dates back to the end of the XIX century. A detailed clinical description of tracheobronchomegaly belongs to the French otolaryngologist P. Mounier-Kuhn (1932). In men, pathology is 4 times more common. At the moment, about 100 cases of the disease have been registered, although their actual number may be significantly higher, since many patients are completely asymptomatic. The age of the manifestation varies from 20 to 40 years.
Causes of Mounier-Kuhn syndrome
In modern pulmonology, Mounier-Kuhn syndrome is mainly considered as a primary congenital anomaly, which is based on systemic connective tissue dysplasia. With this disease, there is dystrophy of the cartilaginous framework and / or underdevelopment of the muscular layer of the tracheobronchial tree (TBT), leading to its gigantic expansion.
Etiologically, tracheobronchomegaly may be associated with pathologies such as Marfan syndrome, Ehlers-Danlos syndrome, elastolysis (flabby skin syndrome), etc. It is assumed that the defect in the structure of TBT is inherited in an autosomal recessive way, as indicated by family observations of tracheobronchomegaly. However, to date, no genetic mutation has been identified, and most of the known cases are sporadic.
Hypotheses are made about possible secondary changes in the tracheobronchial walls with subsequent progression of dilatation during life, which is evidenced by the late age of manifestation of Mounier-Kuhn syndrome. In the literature there are reports of cases of acquired tracheobronchomegaly on the background of:
- respiratory infections (tracheobronchitis, whooping cough);
- diffuse pulmonary fibrosis;
- respiratory distress syndrome in premature newborns who are on a ventilator for a long time;
- congenital immunodeficiency (Louis-Bar syndrome, Bruton’s agammaglobulinemia);
- previous manipulations and surgical interventions on the trachea.
- Irritating and provoking factors can be inhalation of cigarette smoke, toxic industrial gases, polluted air, constant cough.
Pathogenesis
The pathoanatomic basis of the Mounier-Kuhn syndrome is atrophy of elastic fibers and thinning of the smooth muscle layer of the trachea and the main bronchi. This leads to lability of the tracheobronchial walls and a significant fluctuation in the size of the airways during various phases of respiration. Isolated bronchial dilation (bronchomegaly) without tracheomegaly may occur.
During inhalation, negative intra-thoracic pressure increases, which is accompanied by the expansion of the tracheobronchial lumen, during the exhalation phase, the pressure decreases, leading to the collapse of the respiratory tract. With coughing efforts, the walls of the trachea close and vibrate. The weakness of the muscle layer causes the protrusion of the tracheal wall area between the cartilaginous rings and the formation of diverticula.
Bronchial drainage is disrupted, resulting in purulent tracheobronchitis. A constant cough contributes to an increase in intra-bronchial pressure, and after a while bronchiectasis of the distal bronchi, pneumosclerosis, emphysema are formed a second time.
Classification
Depending on the severity of structural changes in TBT, three subtypes of Mounier-Kuhn syndrome are distinguished:
- type 1 – there is a slight symmetrical expansion of the trachea and main bronchi;
- type 2 – marked dilatation and diverticula of the trachea;
- type 3 – the expansion of TBT extends bilaterally to the distal bronchi.
Symptoms of Mounier-Kuhn syndrome
In the absence of bronchopulmonary infection, Mounier-Kuhn syndrome is asymptomatic. The clinical picture usually unfolds in the third or fourth decade of life. The symptoms of tracheobronchomegaly are nonspecific and usually indistinguishable from those caused by chronic tracheobronchitis.
The leading complaint is a chronic debilitating cough with copious purulent sputum. Cough sounds are characterized by a vibrating timbre, reminiscent of the “bleating of a goat”. Because of the many wheezes, breathing becomes noisy, “purring”, audible at a distance. I am worried about shortness of breath, which increases with physical exertion, tightness and pain in the chest, which increases on inspiration, periodic temperature rises. With extensive lesions of TBT, acrocyanosis, deformation of the phalanges of the fingers is noted. Episodes of hemoptysis may occur.
Complications
Against the background of recurrent respiratory infections and persistent cough, patients with Mounier-Kuhn syndrome develop deforming bronchitis, bronchiectasis, tracheobronchomalacia over time. Bullous emphysema of the lungs occurs distal to the altered bronchi. Episodes of spontaneous pneumothorax are possible. COPD, pulmonary hypertension, and chronic respiratory failure are gradually forming. The most common non-respiratory complication is gastroesophageal reflux disease as a consequence of a constant increase in intra-abdominal pressure.
Diagnostics of Mounier-Kuhn syndrome
Examination of patients with suspected Mounier-Kuhn syndrome is carried out in a pulmonological hospital. The auscultative picture is characterized by wet wheezing, vibrating sound in the projection of the trachea with forced breathing and coughing. To confirm tracheobronchomegaly is performed:
- X-ray diagnostics. An overview radiography of the lungs reveals secondary changes in the pulmonary parenchyma, a sharply expanded trachea, the diameter of which is wider than the diameter of the spinal column. To clarify the condition of TBT and the prevalence of the lesion, bronchography is performed. A more accurate X-ray picture is obtained using CT of the lungs, according to which an abnormal expansion of the airways is detected (tracheal diameter > 25-27 mm in men and 21-23 mm in women).
- Bronchoscopy. Tracheobronchomegaly is confirmed by endoscopic examination of TBT. The walls of the trachea are thinned, the mucosa is atrophic and drawn into the inter-cartilaginous spaces (“saw teeth”). In the segmental bronchi, the phenomena of purulent endobronchitis are detected, visualization of tracheal diverticula is possible. During exhalation and coughing, expiratory collapse occurs ‒ the walls of the trachea collapse in the antero-posterior direction. To confirm the morphological diagnosis, a biopsy sample is taken.
- Other studies. To assess the severity of respiratory disorders, spirometry is performed, demonstrating obstructive-restrictive disorders, an increase in residual volume (sometimes spirometric values remain normal). Pulse oximetry, blood gas composition study, bacteriological sputum culture are carried out.
Differential diagnosis
When verifying the Mounier-Kuhn syndrome, other congenital and acquired pathologies of the respiratory tract are excluded:
- tracheomalacia;
- Williams-Campbell syndrome;
- Kartagener syndrome;
- cystic hypoplasia of the lungs;
- foreign bodies of the trachea and bronchi.
Mounier-Kuhn syndrome treatment
Asymptomatic patients with Mounier-Kuhn syndrome do not require special treatment. In case of recurrent bronchopulmonary infections, supportive symptomatic therapy is performed. During periods of exacerbation, antibiotic therapy is carried out, mucolytics, bronchodilators, corticosteroids are prescribed, bronchoalveolar lavage is performed.
To improve the drainage function of TBT, electrophoresis sessions, medicinal inhalations, breathing exercises, percussion massage, postural drainage are shown. Some patients may need noninvasive CPAP ventilation.
Surgical treatment of Mounier-Kuhn syndrome is ineffective. Tracheal stenting and tracheobronchoplastic operations are rarely performed due to the diffuse nature of the lesion. Lung resection often has the opposite effect and causes the progression of tracheobronchomegaly. Lung transplantation also has no proven efficacy in terms of disease prognosis and survival.
Prognosis and prevention
The prognosis depends on the degree and rate of development of respiratory disorders. Recurrent infections of the lower respiratory tract and pulmonary fibrosis have the most significant impact on the quality and duration of life. Prevention recommendations include quitting smoking, minimizing exposure to industrial and occupational irritants, pollutants, and preventing bronchopulmonary infections. Patients with Mounier-Kuhn syndrome are indicated for routine vaccination against influenza and pneumococcal infection.
Literature
- The Mounier-Kuhn syndrome. Milić R, Plavec G, Stojisavljević M, Tomić I, Sarac S. Vojnosanit Pregl. 2010 Oct;67(10):867-70. link
- Mounier-Kuhn syndrome: a rare cause of bronchial dilation. Celik B, Bilgin S, Yuksel C. Tex Heart Inst J. 2011;38(2):194-6. link
- Mounier-Kuhn syndrome (tracheobronchomegaly): An analysis of eleven cases. Akgedik R, Karamanli H, Kizilirmak D, Kurt AB, Öztürk H, Yildirim BB, Çakir L. Clin Respir J. 2018 Mar;12(3):885-889. link
- Tracheobronchomegaly-Mounier-Kuhn syndrome. Al-Mubarak HF, Husain SA. Saudi Med J. 2004 Jun;25(6):798-801. link
- Tracheobronchomegaly–the Mounier-Kuhn syndrome: report of two cases and review of the literature. Van Schoor J, Joos G, Pauwels R. Eur Respir J. 1991 Nov;4(10):1303-6. link