Progression from Near-Normal to End-Stage Lungs in Chronic Interstitial Pneumonia Related to Silica Exposure: Long-Term CT Observations

OBJECTIVE. The objective of our study was to evaluate serial CT changes from normal or near-normal lungs to honeycomb lungs in dust-exposed patients who developed chronic interstitial pneumonia. MATERIALS AND METHODS. From the records of the national hospital for pneumoconiosis, we retrospectively identified patients with chronic interstitial pneumonia who were under surveillance between 1986 and 2006. All patients occasionally underwent chest CT for evaluation of silicosis or exclusion of possible complications. Patients were included in this study only if the initial CT examination did not show obvious chronic interstitial pneumonia. Fourteen patients (all men; median age at initial CT, 58 years) were identified as meeting the inclusion criterion. Two independent reviewers randomly reviewed the CT scans of the study patients to score the extent of ground-glass opacity, reticulation, and honeycombing; to provide a summation of all interstitial opacities (fibrosis score); and to assess coarseness. RESULTS. Autopsy findings were available for eight of the 14 patients and confirmed the usual interstitial pneumonia (UIP) pattern seen on CT. The median follow-up period was 15.4 years, and none of the patients experienced acute exacerbation. One hundred two CT scans were reviewed. The earliest CT abnormalities included faint ground-glass opacity limited to the lung bases (n = 13) or only coarse reticular opacity (n = 1). In 13 patients, fibrosis and coarseness progressed linearly, whereas the other opacities did not. The annual increase of the fibrosis score and coarseness ranged from 0.306% to 4.633% and 0.179 to 0.479, respectively. Honeycombing developed in all patients over a median period of 12.1 years (range, 3.7-19.1 years). CONCLUSION. The coarseness best represented the progression of chronic interstitial pneumonia in dust-exposed patients. The earliest CT finding of a UIP pattern in dust-exposed patients was indistinguishable from other types of chronic interstitial pneumonia.