Manifestations of Mycobacterium avium complex infection

Mycobacterium avium complex (MAC) causes:

• cervical lymphadenitis—more common in children; seek expert paediatric advice
• pulmonary disease, occurring in several forms
  • cavitary and fibrotic upper lobe disease closely resembling tuberculosis—often in older men with pre-existing respiratory disease such as chronic obstructive pulmonary disease
  • progressive bronchiectasis with productive cough, and interstitial or nodular shadowing identified by chest imaging—most common in older women without pre-existing respiratory disease (Lady Windermere syndrome)
  • hypersensitivity pneumonitis—usually follows exposure to aerosols generated by spas that are colonised with nontuberculous mycobacteria (‘hot tub lung’) (see Hypersensitivity pneumonitis). Antibiotic treatment is usually not required
• disseminated disease—occurs in immunocompromised patients, notably those with HIV infection who have a low CD4 cell count (see Disseminated Mycobacterium avium complex infection below).

Some patients who have Mycobacterium avium complex identified by culture of sputum do not need to be treated—see Diagnosis of nontuberculous mycobacterial infections and Approach to managing nontuberculous mycobacterial infections. Clinical assessment by an expert is required.