Pulmonary Fibrosis on High-Resolution CT of Patients With Pulmonary Alveolar Proteinosis

OBJECTIVE. The CT findings of pulmonary fibrosis in patients with pulmonary alveolar proteinosis (PAP) are not yet well defined. The objective of this study was to evaluate the CT findings of PAP with a focus on pulmonary fibrosis secondary to PAP. MATERIALS AND METHODS. High-resolution CT (HRCT) scans of 44 patients with PAP were evaluated retrospectively with a focus on pulmonary fibrosis: 33 patients had autoimmune PAP, and 11 patients had secondary PAP. The intervals between the initial and last CT examinations ranged from 1 to 284 months (median, 60 months). The HRCT images were assessed by two chest radiologists independently; when the two radiologists disagreed, a final decision was made by consensus. RESULTS. A crazy-paving pattern was a more common HRCT finding in patients with autoimmune PAP than in those with secondary PAP. Traction bronchiectasis was found in four patients (9%) on the initial scans and in 10 patients (23%) on the last scans. There was no honeycombing on the initial scans. Honeycombing developed in two patients (5%): It was detected on 2-year follow-up in one patient and on 6-year follow-up in the other patient. Among the patients with autoimmune PAP, those with fibrosis detected on HRCT during follow-up had a worse prognosis than those without fibrosis detected on HRCT (p = 0.041). CONCLUSION. Fibrosis develops in approximately 20% of patients with PAP. The CT findings of parenchymal fibrosis suggest a poor outcome.