CTICasesAutoimmune Interstitial Lung Disease (IPAF / UIP Pattern)
Imaging findings
High-resolution CT demonstrates a basal-predominant, subpleural fibrosing lung disease showing a horizontal straight-line boundary, a four-corner sign (posterior lower lobe and anterior upper lobe disease), and rapid progression to exuberant honeycombing and traction bronchiectasis over two years. The patient had a positive ANA and anti-SSB.
Key takeaways
Although the CT findings in this patient meet the criteria for a usual interstitial pneumonia (UIP) pattern, features such as the "four-corner sign," "straight-line sign," and "exuberant honeycombing" suggest a connective tissue disease-associated ILD or Interstitial Pneumonia with Autoimmune Features (IPAF) rather than idiopathic pulmonary fibrosis (IPF).
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