Morphological and Ultrastructural Analysis of Lung Parenchyma in Patients with Swine Flu Influenza Type A/H1N1
VL Capelozzi, PRM Rocco, ER Parra, HA de Oliveira, M Ximenes, CSV Barbas, MIS Duarte. Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil; Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil; Hospital de Base do Distrito Federal, Brasilia, Brazil; Hospital Israelita Albert Einstein, São Paulo, Brazil
Background: Severe acute respiratory failure due to Swine-Origin Influenza A H1N1 presents a mortality of 9.2%. A better understanding of the underlying mechanisms of this highly lethal new disease can lead to advances in the treatment.
Design: We describe a case series of 3 patients with confirmed diagnosis of H1N1 by positive PCR in nasal swab investigation. All of the patients had acute respiratory failure needing ventilatory support. Morphological assessment and ultrastructural study of lung tissue were performed.
Results: The pathological features were dominated by necrotizing bronchiolitis, diffuse alveolar damage and cytopathic effects. The membranous and respiratory bronchioles were widespread compromised by epithelial necrosis, squamous metaplasia and obliteration by fibroplasia. The parenchyma was modified by extensive alveolar collapse, dilatation of the airspaces, hemorrhage and hyaline membrane formation. Atypical bronchiolar and alveolar epithelial cells were seen in all patients, including multinucleated giant forms, but distinct viral inclusions were not apparent. Ultrastructural analysis showed necrosis and degenerative changes in bronchial and alveolar epithelium with sloughing of the lining cells and denudation of the basement membrane. The regenerating bronchiolar epithelium extended along adjacent alveolar septa showing features of cells with prominent surface microvilli with decreased or absent lamellar bodies and considerable cytologic atypia characterized by nuclear enlargement and clumped nuclear chromatin.The proliferating bronchiolar and alveolar epithelial cells containing tubuloreticular structures and cylindrical confronting cisternae probably representing viral-like particles residuals were distinguished in all cases.
Conclusions: Surgical lung biopsy allows tissue to be sampled for morphological and ultrastructural examination in Swine Flu Influenza A/H1N1 and showed that bronchioles and epithelium, rather than endothelium, are probably the primary target of infection and the diffuse alveolar damage the consequence of airways obliteration, suggesting that the treatment should be focused on the epithelium repair. Financial Support: FAPESP, CNPq.
Wednesday, March 24, 2010 1:00 PM
Poster Session VI # 210, Wednesday Afternoon