대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Microscopic polyangiitis

Radiologic Findings

Fig 1. Chest AP radiograph shows multifocal consolidation superimposed on lower lobe predominant interstitial fibrosis.
Fig 2-4. Chest CT shows bilateral lower lobe predominant traction bronchiectasis and honeycombing with non-subpleural predominance. In the right lung, ill-defined multifocal consolidation with peripheral ground-glass opacities (GGOs) is observed.

Brief Review

Microscopic Polyangiitis (MPA) is a clinicopathologic syndrome characterized by pulmonary and renal involvement, specifically alveolar capillaritis leading to alveolar hemorrhage and necrotizing glomerulonephritis. Serologically, approximately 55 to 65% of patients are positive for MPO-ANCA.
Radiologically, the most frequent manifestation is interstitial pneumonia (IP), predominantly presenting as a UIP pattern. However, distinct from classic idiopathic pulmonary fibrosis (IPF), MPA-associated UIP frequently exhibits atypical minor findings superimposed on the fibrotic background, such as ground-glass opacities (GGO), consolidation, and airway involvement (bronchiolitis, bronchial wall thickening, and bronchiectasis). A particularly characteristic finding is increased attenuation surrounding areas of honeycombing and traction bronchiectasis. This feature correlates pathologically with inflammatory cell infiltration and lymphoid follicles, aiding in the differentiation from idiopathic UIP. Regarding diffuse alveolar hemorrhage (DAH), the principal HRCT findings are diffuse GGO and consolidation. Additionally, poorly defined bilateral centrilobular nodules with ground-glass attenuation, although less common, should prompt consideration of DAH.

References

1. Suzuki A, Sakamoto S, Kurosaki A et al. Chest High-Resolution CT Findings of Microscopic Polyangiitis: A Japanese First Nationwide Prospective Cohort Study. AJR Am J Roentgenol. 2019 Jul;213(1):104-114.
2. Palmucci S, In

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