Cystic bronchiolectasis and airspace enlargement mimicking honeycombing in rheumatoid arthritis-associated interstitial lung disease

A 75-year-old, non-smoker female, with a 31-year history of rheumatoid arthritis (RA) was referred to our hospital for examination of progressive interstitial lung disease (ILD). She had been diagnosed with ILD at the age of 72. Her cough and chest radiology findings had gradually worsened over the past year. High-resolution computed tomography (HRCT) revealed a cluster of cysts at the base of both lungs, which resembled honeycombing observed in idiopathic pulmonary fibrosis (IPF)/usual interstitial pneumonia (UIP). However, these cysts were located slightly away from the pleura and appeared and developed within ground-glass opacity on sequential CT images. In this respect, they appeared to differ from the honeycombing in IPF/UIP. In the pathological examination of surgical lung biopsy specimen, the intralobular bronchioles exhibited cystic dilatation, often involving an entire secondary lobule, caused by destruction in the bronchiolar walls and adjacent alveoli. Airspace enlargement owing to peribronchiolar metaplasia (PBM) was also seen. These findings were thought to correspond to the honeycomb-like appearance on HRCT. In some cases of ILD with UIP in RA patients, the pathogenesis of cystic lesions may differ from that of honeycombing in IPF/UIP.