CTICasesPulmonary AL Amyloidosis with Cystic Destruction
Imaging findings
CT in a middle-aged woman with paraproteinemia demonstrates diffuse bilateral lower lobe predominant cystic and emphysema-like areas of lung destruction associated with ground-glass opacity. Biopsy confirms alveolar septal AL amyloid deposition with Congo red positivity and giant cell reaction. The cystic spaces represent matrix metalloproteinase-driven digestion of lung parenchyma by amyloid-activated macrophages.
Key takeaways
Pulmonary AL (light chain) amyloidosis can present with a diffuse cystic pattern of lung disease mimicking emphysema or cystic ILD on CT. The mechanism involves macrophage-mediated upregulation of matrix metalloproteinases (MMPs) that digest the alveolar interstitium, analogous to neutrophil elastase in emphysema. Congo red staining of biopsy material demonstrates the characteristic apple-green birefringence under polarized light. This presentation may be the first clue to a systemic plasma cell dyscrasia.
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