What is non-tuberculous mycobacterial lung disease?

Non-tuberculous mycobacterial (NTM) lung disease is a chronic lung infection caused by a group of mycobacteria that are found naturally in the environment.

This article provides an expert insight into the symptoms, diagnosis and treatment of NTM lung disease.

What are the symptoms of NTM lung disease?

The symptoms of NTM lung disease are often non-specific and can develop gradually over months or even years. Common symptoms include:

• persistent cough, sometimes accompanied by phlegm or blood
• fatigue and weakness
• shortness of breath
• unexplained weight loss
• chest discomfort
• coughing up blood (known as haemoptysis)

If left untreated, NTM lung disease can cause lung damage and eventually lead to respiratory failure.

What causes NTM lung disease?

NTM lung disease is caused by inhalation of non-tuberculous mycobacteria that are widely present in the soil, water and dust. These bacteria can enter the lungs through breathing in aerosols or coming into contact with contaminated surfaces.

Unlike tuberculosis, which is caused by the bacterium Mycobacterium tuberculosis, NTM lung disease isn’t contagious and doesn’t spread from person to person. In fact, exposure to non-tuberculous mycobacteria is quite common and most people with healthy immune systems aren’t affected.

However, certain factors can increase the risk of developing NTM lung disease. People with underlying lung conditions, such as chronic obstructive pulmonary disease (COPD), bronchiectasis or cystic fibrosis, are particularly vulnerable. In addition, older adults and people with a history of smoking are at a higher risk.

How is NTM lung disease diagnosed?

Your respiratory physician will begin with a detailed review of your medical history and symptoms. Chest imaging, such as chest X-rays or high-resolution computed tomography (HRCT) scans, will then be conducted to identify abnormalities in the lungs, such as nodules, cavities or areas of bronchiectasis.

After, sputum samples or bronchial washings will be analysed to detect the presence of NTM bacteria. Culture tests will also help identify the specific species of mycobacteria involved, as this may influence treatment decisions. In some cases, pulmonary function tests will be performed to evaluate lung capacity.

What is the treatment for NTM lung disease?

Treatment for NTM lung disease requires a multi-drug antibiotic regimen. This usually includes macrolides, such as clarithromycin or azithromycin, in combination with other antibiotics like ethambutol and rifampin.

The duration of treatment typically lasts 12-18 months or longer. This extended period is necessary because NTM bacteria are slow-growing and can be resistant to treatment. To ensure the infection is fully eradicated, treatment continues for at least 12 months after sputum cultures become negative.

In some cases, adjunct therapies may be recommended, such as:

• Airway clearance techniques to remove mucus and reduce bacterial load.
• Management of underlying conditions like COPD or bronchiectasis.
• Surgery, in rare cases, to remove severely damaged or infected lung tissue.

Follow-up visits are typically scheduled every 1-3 months during active treatment. Physical examinations, sputum tests and imaging studies will be performed during these appointments to monitor the infection’s status and detect any potential complications. Once treatment is complete, periodic follow-ups will be arranged to monitor for any recurrence.