Two patterns: nodular bronchiectatic (middle lobe and lingula bronchiectasis with tree-in-bud, often in older women) and fibrocavitary (upper lobe cavities like TB in men with COPD) — separating it from TB matters for treatment and isolation.
Orient first
- Mycobacterium avium complex is commonest; diagnosis needs repeated positive sputum cultures (ATS/IDSA criteria — verify).
- The nodular bronchiectatic form is slowly progressive; the cavitary form is more aggressive.
- In endemic TB regions, NTM is underdiagnosed as "treatment-failure TB".
Acquire the study
- Non-contrast CT chest, thin sections (≤ 1.25 mm), lung window, with expiratory images optional.
The manoeuvre
- Lung window: bronchiectasis in the middle lobe and lingula; wall thickness and mucus plugging.
- Tree-in-bud nodules and centrilobular nodules in the same distribution.
- Upper lobe cavities: wall thickness in mm; pleural thickening.
- Compare with prior CT over an interval of months — slow progression favours NTM.
What confirms it
- Typical CT pattern with repeated positive cultures meeting the criteria.
What licenses you to exclude it
- Imaging cannot separate NTM from TB reliably — microbiology decides.
The classic misread
- Calling middle lobe bronchiectasis from another cause NTM without cultures.