Illustration of an enlarged trachea compared to normal-sized bronchi, representing Mounier-Kuhn Syndrome

Unmasking Mounier-Kuhn Syndrome: When a Rare Condition Mimics Common Lung Diseases

Avery Sinclair in Health & Wellness August 2025 • 4 min read.

"Learn how this often-misdiagnosed condition can lead to recurrent respiratory issues and bronchiectasis, and why early detection is key."

Imagine a condition so rare, it's often missed, masquerading as a run-of-the-mill lung problem. That's Mounier-Kuhn Syndrome (MKS), a condition characterized by an abnormally large trachea and main bronchi. Radiologically, it manifests by marked dilatation of the trachea and main bronchi and symptomatically early in life with recurrent bronchopulmonary infection and bronchiectasis.

MKS isn't just a curiosity; it's a real challenge for those affected. The hallmark of this syndrome is tracheobronchomegaly, weakening and dilation of the trachea and major bronchi. This structural change can lead to a cascade of respiratory issues, making individuals more susceptible to infections and lung damage.

In this article, we'll delve into a case that highlights the importance of recognizing MKS, particularly when it presents later in life. We'll explore how this rare condition can be mistaken for more common respiratory ailments and discuss the diagnostic steps that can lead to accurate identification and appropriate management.

The Case: When Recurrent Infections Hint at Something More

Illustration of an enlarged trachea compared to normal-sized bronchi, representing Mounier-Kuhn Syndrome

Consider a 68-year-old male, a former smoker with a history of recurrent lung infections, excessive sputum production, fever, and worsening dyspnea. He was hospitalized repeatedly for treatment of recurrent bronchopulmonary infection characterized by excessive sputum production, fever and worsening dyspnea. He was an ex-smoker with 36 pack-year smoking history.

His medical history included emphysema and bronchiectasis, common conditions often associated with smoking and chronic respiratory issues. However, despite treatment for these conditions, his symptoms persisted, raising suspicion for an underlying, less common cause.

During his examination, key findings emerged:

Significant dilation of the trachea (40mm) and main bronchi (28mm each)
Fiberoptic bronchoscopy revealed an elliptically shaped, dilated trachea with dynamic airway changes during suctioning and coughing.

These findings, coupled with the patient's history of recurrent infections, led to a diagnosis of Mounier-Kuhn Syndrome. The diagnosis is made by CT: diagnostic criteria are tracheal diameter >30mm, right bronchial diameter >24mm and left bronchial diameter >23mm. The patient was prescribed chest percussive device to promote mobilization of respiratory secretions to reduce recurrent bronchopulmonary infections.

What This Means for You

Mounier-Kuhn syndrome, while rare, underscores the importance of considering less common diagnoses in patients with persistent respiratory issues. If you or someone you know experiences recurrent lung infections, especially with known lung conditions, it's crucial to discuss the possibility of MKS with a healthcare provider.

Early diagnosis can lead to targeted management strategies, such as chest physiotherapy and antibiotics during infections, potentially improving quality of life and preventing further lung damage. In severe cases, tracheal stenting or tracheobronchoplasty may be considered.

Remember, knowledge is power. By increasing awareness of rare conditions like MKS, we can empower individuals to seek appropriate medical care and improve their health outcomes.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.chest.2018.08.526, Alternate LINK

Title: Mounier-Kuhn Syndrome: A Rare Cause Of A Common Disease

Subject: Cardiology and Cardiovascular Medicine

Journal: Chest

Publisher: Elsevier BV

Authors: Nabil Mesiha, Ankur Mogla, Mona Alipour, Jennifer Chiu, Viswanath Vasudevan, Farhad Arjomand, Louis Gerolemou

Published: 2018-10-01

Everything You Need To Know

What exactly is Mounier-Kuhn Syndrome?

Mounier-Kuhn Syndrome (MKS) is a rare condition characterized by an abnormally enlarged trachea and main bronchi, leading to a weakening and dilation of these airways. This structural change makes individuals more susceptible to recurrent respiratory infections and can cause bronchiectasis, the irreversible widening of the airways. The enlargement is often radiologically visible and the diagnosis is made by CT scan.

Why is it important to diagnose Mounier-Kuhn Syndrome?

The significance of diagnosing Mounier-Kuhn Syndrome (MKS) lies in its impact on the respiratory system. MKS can often be mistaken for more common lung conditions, leading to delayed or inappropriate treatment. Early and accurate identification of MKS is crucial because it allows for targeted management strategies, such as chest percussive devices, to help reduce recurrent bronchopulmonary infections and improve quality of life.

How is Mounier-Kuhn Syndrome typically diagnosed?

Diagnostic steps for Mounier-Kuhn Syndrome (MKS) involve a combination of clinical evaluation and imaging techniques. A patient history of recurrent respiratory infections, excessive sputum production, and dyspnea should raise suspicion. Imaging such as a CT scan is vital for confirming the diagnosis, as it can reveal the characteristic dilation of the trachea and main bronchi. In some cases, fiberoptic bronchoscopy may also be used to observe the airways.

What are the potential implications of having Mounier-Kuhn Syndrome?

The implications of Mounier-Kuhn Syndrome (MKS) extend beyond the physical symptoms. Recurrent infections and bronchiectasis, common in MKS, can lead to significant morbidity and reduced quality of life. The chronic nature of the condition necessitates long-term management. This can include strategies to manage and mobilize secretions, prevent infections, and address any associated complications. Without proper management, the disease can progressively worsen.

When should someone consider the possibility of Mounier-Kuhn Syndrome?

If someone experiences recurrent lung infections and has known lung conditions, discussing the possibility of Mounier-Kuhn Syndrome (MKS) with a healthcare provider is important. Persistent symptoms, especially when common treatments aren't effective, should prompt further investigation. The patient mentioned in the text, a 68-year-old male, a former smoker, whose symptoms persisted despite treatment for conditions like emphysema and bronchiectasis, required the consideration of less common causes such as MKS.