CTICasesCavitary Mycobacterium avium complex (MAC) Infection
Imaging findings
Historical chest radiograph from six years prior demonstrates emphysema, apical pleural thickening, and calcified granulomas. A follow-up chest radiograph shows a new cavitary lesion in the right lung apex. Subsequent chest CT confirms a confluent cluster of thick-walled cavities in the right apex, some of which contain small fluid levels. There is associated tree-in-bud nodularity and bronchiolectasis in the surrounding lung parenchyma, representing downstream endobronchial spread of infection, in the setting of moderate background centrilobular and paraseptal emphysema.
Key takeaways
Mycobacterium avium complex (MAC) infection can manifest as a classic fibrocavitary upper lobe disease, particularly in older male smokers with pre-existing lung disease such as emphysema. Pre-existing architectural abnormalities, such as apical scarring, bullae, or calcified granulomas from remote granulomatous disease, impair normal mucociliary clearance and facilitate mycobacterial colonization and subsequent tissue destruction. This cavitary form of MAC is progressive and typically requires long-term multi-drug antibiotic therapy.
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