Confocal Laser Endomicroscopy for Diagnosis and Monitoring of Pulmonary Alveolar Proteinosis

Background: The diagnosis of pulmonary alveolar proteinosis (PAP) is based on computed tomography, histology, and antibodies to granulocyte-macrophage colony-stimulating factor. The role of a novel technique for imaging cells and elastin during endoscopy, probe-based confocal laser endomicroscopy (pCLE), has not yet been investigated in PAP patients. The aim of the present study was to estimate the value of pCLE in the PAP diagnosis and treatment in comparison with the findings of high-resolution computed tomography (HRCT) before and after whole-lung lavage. Methods: In vivo pCLE was performed during bronchoscopy in 6 male patients with PAP before and after whole-lung lavage. In certain lung segments, pCLE was followed by HRCT. Results: During the in vivo pCLE, we found characteristic signs of PAP: a fluorescent floating amorphous substance in the alveoli lumen sticking to conglomerates along with alveolar macrophages. These features were present to a lesser extent after a whole-lung lavage. pCLE revealed specific PAP features not only in segments with crazy-paving and ground-glass opacity, but also in segments without HRCT findings. Conclusions: The alveolar imaging in PAP patients is able to reveal characteristic changes, both in the presence and in the absence of HRCT findings. Therefore, pCLE may be a helpful tool for the diagnosis and whole-lung lavage therapy. Our data prove that accumulation of lipoproteinaceous substances within the alveoli at PAP is a diffuse but not a patchy process.