Post-COVID Interstitial Lung Disease

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RSNA Case Collection


Post-COVID Interstitial Lung Disease :
The acute phase of COVID-19 pneumonia manifests with bilateral peripheral ground-glass opacities and consolidations on chest CT that are distributed throughout lung zones, but located predominantly in subpleural areas and in the lung bases. The residual findings are located in the same areas as acute findings and include fibrotic bands with traction bronchiectasis. This patient had confirmed COVID-19 infection testing 2 weeks before presentation, the typical rapid onset of fibrosis and bronchiectasis within 6 months of admission, and presence of fibrotic-like changes in the same lung areas as the initial CT findings. Together, these support the diagnosis of post-COVID interstitial lung disease (PCILD).

Differential diagnoses:Nonspecific Interstitial Pneumonitis :
Nonspecific interstitial pneumonia (NSIP) is an interstitial lung disease associated with several connective tissue and autoimmune disorders. The typical CT findings include GGO that are bilateral and symmetrical, subpleural, often with basal predominance. A specific finding of NSIP is immediate subpleural sparing of the lungs, whereas PCILD demonstrates lower-lobe predominance and includes subpleural fibrotic bands. The fibrotic type of NSIP is also characterized by fine reticular opacities, traction bronchiectasis, and loss of volume in the lower lobes. While this case shows subpleural sparing, the clinical context of known COVID-19 infection makes PCILD more likely.Fibrosing Hypersensitivity Pneumonitis :
Fibrotic hypersensitivity pneumonitis (fHP) is an immune-mediated disorder that causes inflammation and fibrosis of the lung parenchyma and small airways. The typical CT findings include coarse reticulations, often with a middle or upper-zone predominance. The parenchymal changes in PCILD are lower-lobe predominant and spare the lung apices. The most specific finding for fHP is the "headcheese sign" or "three-density sign," which describes a combination of GGO, hyperlucent lung, and normal lung tissue in close proximity. Other findings include mediastinal lymphadenopathy and ill-defined centrilobular nodules.