Pulmonary fibrosis in pulmonary alveolar proteinosis evaluated by transbronchial lung cryobiopsy: A single-center retrospective study

Abstract

Background: Approximately 20% of patients with pulmonary alveolar proteinosis (PAP) present with pulmonary fibrosis on high-resolution computed tomography (HRCT). Although transbronchial lung cryobiopsy (TBLC) has recently been used to diagnose fibrotic interstitial lung disease, no studies have investigated whether TBLC is useful for the histopathological detection of pulmonary fibrosis coexisting with PAP. Therefore, the present study aimed to investigate the utility of TBLC for evaluating pulmonary fibrosis in patients with PAP.

Methods: We retrospectively reviewed patients diagnosed with PAP who underwent TBLC at our hospital between May 2021 and March 2023. We collected data including patient background, HRCT findings, and histopathological findings of the TBLC samples.

Results: Seven patients met the inclusion criteria, with a median age was 69 years; 5 patients were male. Six patients were diagnosed with autoimmune PAP, and one was diagnosed with unclassified PAP. Periodic acid-Schiff staining-positive materials in the alveoli were observed in six out of seven patients. Pulmonary fibrosis, defined as fibrosis with architectural distortion, was found in two patients. Fibroblastic foci and airway-centered fibrosis were presented in two and one patient, respectively. As a result of a multidisciplinary discussion, we diagnosed one each with fibrotic HP coexisting with PAP and PAP-associated fibrosis.

Conclusion: Two of the seven patients with PAP presented histopathologically with pulmonary fibrosis in samples obtained through TBLC. Thus, TBLC should be considered when the coexistence of pulmonary fibrosis is suspected.

Keywords: Fibroblastic foci; Fibrotic hypersensitivity pneumonitis; Pulmonary alveolar proteinosis; Pulmonary fibrosis; Transbronchial lung cryobiopsy.