CTICasesCystic Lung Disease in Connective Tissue Disease Overlap Mimicking UIP
Imaging findings
Chest CT shows severe cystic changes in the lower lobes, mimicking the honeycombing of usual interstitial pneumonia (UIP). However, there is a striking absence of reticulation, architectural distortion, or traction bronchiectasis in the remaining lung parenchyma, which is completely normal. The cysts are thin-walled and run along the airways, consistent with airway-derived cysts (bronchiolitis-associated) rather than true fibrotic honeycombing. Serology was positive for both anti-SSA (Sjögren's) and anti-Jo-1 (anti-synthetase syndrome).
Key takeaways
Progressive lower-lobe thin-walled cysts can closely mimic the honeycombing of UIP on CT. This 'pseudo-honeycombing' can occur in connective tissue diseases (such as Sjögren's syndrome or anti-synthetase syndrome) due to lymphoid follicular bronchiolitis or light chain deposition, where cysts are derived from dilated airways rather than a matrix of dense fibrosis. Identifying the lack of surrounding fibrosis/reticulation and checking autoimmune serology are critical, as these patients benefit from immunosuppressive therapy rather than antifibrotics.
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