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Legionnaires' disease pneumonia: histopathologic features and comparison with microbial and chemical pneumonias
Abstract:
The histopathologic findings in lung tissue are reported from five cases of Philadelphia Legionnaire's Disease and the results are compared to pneumonias caused by other microbial and chemical agents. Histopathology of lung tissue was similar in all cases, despite the fact that death occurred between the fourth and 14th day of clinical illness. The inflammatory response was almost totally limited to the lower respiratory tract and primarily involved respiratory bronchioles, alveolar ducts and alveoli. Major bronchial branches and pulmonary interstices showed little or no involvement. There was considerable variation in the extent and nature of the consolidation, but the overall reaction pattern was highly characteristic of diffuse alveolar damage. Most involved areas showed intra-alveolar, fibrinocellular mononuclear cell predominant exudates, associated with pneumonocytic hyperplasia and slough. These findings plus the presence of erythroleucophagocytosis by macrophages and paucity of polymorphonuclear leucocytes are commonly associated with psittacine pneumonia, and much less so with classic patterns of bacterial, viral, fungal or rickettsial pneumonias. Of the toxic inhalants, nickel carbonyl, phosgene, nitrous oxide, cadmium oxide and some halogenated hydrocarbons have been associated with this tissue reaction pattern. Bacteria were notably absent in lung tissue stained by methods used to demonstrate the Legionnaires' Disease agent.
Insights
Histopathology of lung tissue in Legionnaire's Disease shows diffuse alveolar damage, distinct from typical bacterial or viral pneumonias. This pattern resembles psittacine pneumonia and reactions to certain toxic inhalants.
Area of Science:
- Pulmonary Pathology
- Infectious Disease
- Toxicology
Background:
- Legionnaire's Disease is a severe pneumonia with varied histopathologic presentations.
- Previous studies have not fully characterized the specific lung tissue changes in Legionnaire's Disease.
Purpose of the Study:
- To describe and compare the histopathologic findings in lung tissue from five cases of Legionnaire's Disease.
- To differentiate Legionnaire's Disease lung pathology from other causes of pneumonia.
Main Methods:
- Histopathologic examination of lung tissue from five fatal cases of Legionnaire's Disease.
- Comparison of findings with known patterns of microbial and chemical pneumonias.
Main Results:
- Histopathology revealed diffuse alveolar damage predominantly affecting lower respiratory tract structures.
- Exudates were mononuclear cell-predominant with pneumonocytic hyperplasia and erythroleucophagocytosis.
- Findings were dissimilar to typical bacterial, viral, fungal, or rickettsial pneumonias, but shared features with psittacine pneumonia and toxic inhalant injury.
- Bacteria were absent in stained lung tissue.
Conclusions:
- The lung histopathology in Legionnaire's Disease is characteristic of diffuse alveolar damage with specific features.
- This pattern is more closely aligned with psittacine pneumonia and toxic inhalant reactions than with common infectious pneumonias.
- Histopathology can aid in distinguishing Legionnaire's Disease from other pulmonary conditions.