AbstractWe present the clinical, radiological, and pathological findings of open lung biopsies from monozygotic prematurely born male twins with respiratory distress at ages 6 and 8 weeks postnatally. Radiological examination showed a reticular nodular interstititial pattern on chest radiography. High‐resolution computed tomography (HRCT) revealed ground‐glass opacification and thickened interstitial septae in both infants. Lung biopsies showed a similar histology. There was diffuse interstitial thickening of the alveolar septa by mesenchymal cells, without prominent hyperplasia of type 2 pneumocytes, and without airspace exudates. Sections were periodic acid‐Schiff (PAS)‐positive within the cytoplasm of interstitial cells, indicating the presence of glycogen. Thus the diagnosis of pulmonary interstitial glycogenosis was made. Both infants were treated with glucocorticoids and had a favorable outcome. We speculate that pulmonary interstitial glycogenosis could be a histopathological form of chronic lung disease (CLD) of infancy. Pediatr Pulmonol. © 2005 Wiley‐Liss, Inc.