What is Mounier-Kuhn syndrome?
Mounier-Kuhn syndrome, also called tracheobronchomegaly, is a rare condition in which the trachea (windpipe) and main bronchi are much wider than normal. The elastic fibres and smooth muscle in the airway wall are thinned or missing, so the walls are weak and floppy.
The enlarged airways cause two main problems. First, the weakened walls tend to collapse when breathing out or coughing, so the cough is ineffective. Second, pockets (diverticula) form between the cartilage rings where mucus collects. Together these lead to pooling of secretions, repeated chest infections and, over time, bronchiectasis.
The condition is most often diagnosed in men in their thirties and forties, although it may be found at any age. Many people have had a lifelong cough before the diagnosis is made.
Symptoms
Symptoms range from none at all to severe, recurrent lung infection. Common features include:
- A loud, harsh or ineffective cough, sometimes described as a honking or barking cough
- Large amounts of sputum, often daily
- Repeated chest infections and pneumonia
- Breathlessness on exertion
- Wheeze or noisy breathing
- Coughing up blood during infections
Because these symptoms overlap with chronic bronchitis, COPD, asthma and post-tuberculosis lung damage, the condition is often missed for years.
Causes and associations
Mounier-Kuhn syndrome is thought to result from a congenital weakness of the connective tissue in the large airways, although it may only become apparent in adult life. It has been reported alongside connective tissue disorders such as Ehlers-Danlos syndrome and cutis laxa. Similar airway widening can also develop after long-term mechanical ventilation, in advanced lung fibrosis, and with long-standing cigarette smoking. Smoking and recurrent infection accelerate airway damage.
How Mounier-Kuhn syndrome is diagnosed
The diagnosis is made by measuring the width of the airways on CT, supported by bronchoscopy.
| Test | What it shows |
|---|---|
| CT chest (inspiratory and expiratory) | Widening of the trachea and main bronchi beyond accepted size limits, diverticula, bronchiectasis and collapse of the airway on breathing out |
| Flexible bronchoscopy | The enlarged, floppy airway with diverticula, the degree of dynamic collapse, and samples for culture |
| Lung function tests | Airflow obstruction and an enlarged dead space |
| Sputum culture, including for mycobacteria | Bacteria such as Pseudomonas, and exclusion of tuberculosis or non-tuberculous mycobacteria |
| Blood tests for bronchiectasis causes | Immune deficiency, allergic bronchopulmonary aspergillosis and other treatable contributors |
Other causes of bronchiectasis such as cystic fibrosis, primary ciliary dyskinesia and previous tuberculosis are considered, as they are more common and change management.
Treatment
There is no treatment that restores the airway wall, so management focuses on keeping the airways clear and preventing infection, in the same way as bronchiectasis.
Airway clearance
Daily chest physiotherapy, taught by a respiratory physiotherapist, is the foundation of care. Techniques include the active cycle of breathing, oscillating positive expiratory pressure devices and postural drainage. Nebulised saline may help loosen thick secretions.
Infection control
- Prompt antibiotic courses guided by sputum culture
- Long-term macrolide or inhaled antibiotic treatment for people with frequent exacerbations
- Influenza and pneumococcal vaccination
- Complete stopping of smoking
Treatment of airway collapse
When severe expiratory collapse causes significant symptoms, options include non-invasive positive pressure (CPAP) to splint the airway, and in selected patients airway stenting by interventional bronchoscopy. Stents can cause complications such as mucus plugging and migration, so they are considered carefully, sometimes after a short trial. Surgical airway support (tracheobronchoplasty) and lung transplantation are reserved for rare, severe cases and are planned with thoracic surgery and transplant centres.
Outlook and living with Mounier-Kuhn syndrome
The outlook varies. Some people have mild, stable disease for decades, while others develop progressive bronchiectasis with frequent infections. Consistent airway clearance, early treatment of infections and avoiding smoking make a meaningful difference. Regular follow-up includes sputum surveillance, lung function testing and periodic review of the airway.
When to seek urgent care
Seek urgent medical help for coughing up more than a small amount of blood, breathlessness at rest, high fever with increased or discoloured sputum, chest pain, or confusion and drowsiness during a chest infection.
Frequently asked questions
Is Mounier-Kuhn syndrome the same as bronchiectasis?
Not exactly. Mounier-Kuhn syndrome is widening of the trachea and main bronchi due to a weak airway wall. It often leads to bronchiectasis in the smaller airways, and the treatment is similar.
Can Mounier-Kuhn syndrome be cured?
No treatment restores the airway wall, but airway clearance, early treatment of infection and, where needed, airway support can control symptoms and reduce lung damage.
Why is my cough so ineffective?
The weak airway walls collapse when you cough, so air cannot move fast enough to carry mucus upwards. Physiotherapy techniques are designed to move mucus without relying on forceful coughing.
Will I need a stent?
Most people do not. Stents are considered only when severe airway collapse causes significant symptoms despite other treatment, because stents carry their own risks.
Is the condition inherited?
It may have a congenital basis and is sometimes seen with inherited connective tissue disorders, but most people have no affected relatives.
Can I continue to work and exercise?
Most people can. Regular exercise helps clear mucus and maintain fitness. Avoiding smoke and dusty environments is advisable.
Related conditions and procedures
Consult Dr. Gogineni Ratnakara Rao
Apollo Hospitals, Financial District: Monday to Saturday, 8:30 AM to 5:00 PM. Anything in Lung Clinic, Chanda Nagar: Monday to Saturday (Thursday closed), 6:00 PM to 9:00 PM.