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.

Clinical presentation

Some patients are relatively asymptomatic. However, most have a combination of respiratory and systemic features similar to tuberculosis;

• chronic cough
• shortness of breath on exertion
• haemoptysis
• low-grade fever
• night sweats
• fatigue
• weight loss

Pathology

As with M. tuberculosis NTMs commonly cause pulmonary infection.

More than 150 species of NTM species are identified some of which have been can cause infections in humans. These organisms include:

• Mycobacterium avium-intracellulare: ~60% (on bronchial secretions)
  • see: pulmonary MAIC infection
• Mycobacterium kansasii: ~25%
• Mycobacterium fortuitum
• Mycobacterium malmoense: pulmonary Mycobacterium malmoense infection
• Mycobacteriumgordonae
• Mycobacterium szulgai
• Mycobacterium scrofulaceum / Mycobacterium parascrofulaceum
• Mycobacterium xenopi
• Mycobacterium chelonae: pulmonary Mycobacterium chelonae infection
• Mycobacterium simiae
• Mycobacterium palustre
• Mycobacterium kumamotonense
• Mycobacterium kubicae
• Mycobacterium morokaense
• Mycobacterium abscesssus: pulmonary Mycobacterium abscessus infection ²

Risk factors

• chronic lung diseases such as ¹²
  • asthma
  • COPD
  • alpha-1 antitrypsin deficiency
  • pneumoconioses
  • non-CF bronchiectasis
  • primary ciliary dyskinesia
  • allergic bronchopulmonary aspergillosis
• older age and tall slim Caucasian females seem to be more susceptible
• immunodeficiency states ¹²
  • inherited disorders of IFNγ-IL12 pathway (eg, IFNγR1 mutations)
  • other cytokine signalling 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-oesophageal reflux disease (GORD)

Associations

There may be an association achalasia of gastric cardia and M. fortuitum/chelonae infection.

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