Pulmonary Interstitial Glycogenosis: Review of Histopathologic, Immunocytochemical and Ultrastructural Features.
John Hicks, Claire Langston, Eric Wartchow, Gary Mierau. Texas Children's Hospital & Baylor College of Medicine, Houston; The Children's Hospital, Denver, CO
Background: Pulmonary interstitial glycogenosis (PIG) is a recently described idiopathic childhood interstitial lung disease, based upon identifying glycogen-laden mesenchymal cells in the alveolar interstitium. PIG may be an isolated finding, or associated with disorders of deficient lung growth or development (up to 40% of cases). Infants with PIG tend to have a more favorable prognosis with or without corticosteroid therapy compared with children with chronic pneumonitis of infancy.
Design: Pathology archive review of 2 pediatric hospitals identified 18 infants that were diagnosed with PIG. The study population was comprised of 10 females and 8 males with an age range of 2 weeks to 4 months. The typical clinical scenario was tachypnea, hypoxemia, and diffuse interstitial infiltrates with overinflated lungs on radiologic examination. The lung biopsies from these patients had routine histologic examination, PAS and PAS-diastase staining, vimentin and CD68 immunostaining, and electron microscopic examination performed.
Results: The lung biopsies typically showed alveolar interstitial widening with increased cellularity. The increased cellularity was not due to inflammatory cells, but associated with intersitial mesenchymal cells. These cells were immunoreactive with vimentin, and lacked CD68 reactivity and were not histiocytes. Typically, PAS positive, diastase-sensitive material indicative of glycogen was noted within the cytoplasm of interstitial mesenchymal cells. However, the detection by PAS was inconsistent, most likely due to loss of glycogen with formalin fixation. Electron microscopy demonstrated readily that the spindle-shaped intersitial cells were engorged with monoparticulate glycogen and accounted for the interstitial widening. Other findings included concomitant lung injury or remodeling associated with alveolar growth abnormalities.
Conclusions: PIG is associated with glycogen accumulation in the interstitial mesenchymal cells and has been postulated to represent an abnormality of lung cytodifferentiation or interstitial cell maturation. There is no association with systemic glycogen storage disease. Ultrastructural examination can facilitate recognition of PIG. PIG should be considered with an neonate or infant that has a bronchopulmonary-like clinical presentation when intubation is not necessary and when infectious and inflammatory etiologies have been excluded. It is important to recognize PIG because it tend to have a more favorable outcome than chronic pneumonitis of infancy.
Wednesday, March 2, 2011 9:30 AM
Poster Session V # 281, Wednesday Morning