Figure 5b. Alveolar proteinosis in a 37-year-old woman with a nonproductive cough and dyspnea. (a) Posteroanterior chest radiograph shows bilateral reticular areas of increased opacity, which occur predominantly in the lower zones. (b) High-resolution CT scan shows diffuse geographic ground-glass attenuation with superimposed intra- and interlobular septal thickening (arrowhead). Note the polygonal appearance, which represents the secondary pulmonary lobule. (c, d) Photomicrographs (original magnification, x400; hematoxylin-eosin [c] and periodic acid-Schiff [d] stains) of a specimen from transbronchial biopsy show alveolar spaces filled by a dense, eosinophilic, granular proteinaceous material (*) that is positive for periodic acid-Schiff stain.