Categories
Internal Medicine

Mycobacterium avium complex (MAC) infection

Mycobacterium avium complex consists of multiple nontuberculosis mycobacterial species (NTM), which cannot be distinguished in the microbiology laboratory and requires genetic testing.

Mycobacterium avium complex consists of multiple nontuberculosis mycobacterial species (NTM), which cannot be distinguished in the microbiology laboratory and requires genetic testing.

  • M/C cause of NTM pulmonary disease ((80%) worldwide

Aetiology

Risk factors:

  • Malignancy: Lung cancer
  • Immunosuppression: HIV/AIDS, organ transplantation
  • Structural pulmonary disease: Chronic obstructive pulmonary disease (COPD) and bronchiectasis

Non-tuberculous mycobacterium (NTM):

  • Mycobacterium avium complex (MAC): Multiple NTMs, which cannot be distinguished in the microbiology laboratory and requires genetic testing
  • Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium abscessus complex

Clinical features

Pulmonary disease (NTM-PD) (M/C manifestation):

  • Malaise, cough, weakness, dyspnea, and occasional hemoptysis

Diagnosis

trd-82-15-g001
Treatment initiation algorithm for treatment naïve MAC-PD. Treatment should be considered when patients have risk factors for disease progression, including cavitary lesion(s), low body mass index, poor nutritional status, extensive disease, and AFB smear-positive sputum. If patients have mild disease and no risk factors for progression, treatment should be initiated when patients exhibit disease progression. MAC-PD: Mycobacterium avium complex pulmonary disease; HRCT: high-resolution computed tomography; AFB: acid-fast bacilli. | Kwon, Y. S., Koh, W. J., & Daley, C. L. (2019). Treatment of Mycobacterium avium Complex Pulmonary Disease. Tuberculosis and respiratory diseases, 82(1), 15–26. doi:10.4046/trd.2018.0060

Imaging:

  • Fibrocavitary form: Cavitary lesion in the upper lobes and is usually associated with other pulmonary diseases
  • Nodular bronchiectatic form: Bilateral bronchiectasis with multiple nodules and tree-in-bud opacities often in the right middle lobe and the lingular segment of the left upper lobe on high-resolution computed tomography (HRCT)

Management

  • Macrolides (clarithromycin/azithromycin) + rifampin + ethambutol (12 months after negative sputum culture conversion)

Poor prognosis:

  • Low body mass index
  • Poor nutritional status
  • Presence of cavitary lesion(s)
  • Extensive disease
  • Positive acid-fast bacilli smear

Leave a Reply