Pulmonary non-tuberculous mycobacterial infection

Pulmonary non-tuberculous mycobacterial (NTM) infection refers to pulmonary infection caused by one of the large number (at least 150) mycobacterial species other than Mycobacterium tuberculosis. However, certain species are much more common than others.

Epidemiology

Risk factors

• chronic lung diseases such as ¹²:

  • asthma

  • COPD

  • alpha-1 antitrypsin deficiency

  • cystic fibrosis (CF)

  • pneumoconioses

  • non-CF bronchiectasis

  • primary ciliary dyskinesia

  • allergic bronchopulmonary aspergillosis

• older age and tall slim white females seem to be more susceptible

• immunodeficiency states ¹²

  • inherited disorders of IFNγ-IL12 pathway (e.g. IFNγR1 mutations)

  • other cytokine signaling disorders (e.g. STAT mutations)

  • macrophage and dendritic cell function disorders (e.g. GATA2 and NRAMP)

  • acquired immunodeficiencies (HIV-AIDS)

  • functional anti-interferon gamma antibodies

• gastro-esophageal reflux disease (GERD)

Associations

There may be an association between achalasia of the gastric cardia and Mycobacterium fortuitum/chelonae infection.

Clinical presentation

Some patients are relatively asymptomatic. However, most have a combination of respiratory and systemic features that may resemble pulmonary tuberculosis:

• chronic cough

• shortness of breath on exertion

• hemoptysis

• low grade fever

• night sweats

• fatigue

• weight loss

Pathology

As with Mycobacterium tuberculosis, non-tuberculous mycobacteria (NTM) commonly cause pulmonary infections. More than 150 species of NTM species have been identified, some of which can cause infections in humans. These include:

• Mycobacterium abscessus: pulmonary Mycobacterium abscessus infection ²

• Mycobacterium avium-intracellulare (MAI): ~60% (on bronchial secretions)

  • see: pulmonary MAIC infection

• Mycobacterium chelonae: pulmonary Mycobacterium chelonae infection

• Mycobacterium chimaera: pulmonary Mycobacterium chimaera infection

• Mycobacterium fortuitum

• Mycobacterium gordonae

• Mycobacterium kansasii: ~25%

• Mycobacterium kubicae

• Mycobacterium kumamotonense

• Mycobacterium malmoense: pulmonary Mycobacterium malmoense infection

• Mycobacterium morokaense

• Mycobacterium palustre

• Mycobacterium scrofulaceum / Mycobacterium parascrofulaceum: pulmonary Mycobacterium parascrofulaceum infection

• Mycobacterium simiae

• Mycobacterium szulgai

• Mycobacterium xenopi

Treatment and prognosis

Detailed guidelines on the management approach are available ¹². The general principles are:

• multidrug therapy according to the sensitivities of the organisms

• treatment for at least 12 months

• specialist follow-up to monitor compliance and drug side-effects