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Pulmonary pathology of Rocky Mountain spotted fever (RMSF) in children
Abstract:
Despite infrequent respiratory symptoms, histopathologic changes were identified in the lungs of 15 of 16 children dying of Rocky Mountain spotted fever (RMSF). Gross examination demonstrated increased lung weight, edema, congestion, focal hemorrhage, and bronchopneumonia in a few cases. Paraffin sections were stained with hematoxylin and eosin and phosphotungstic acid-hematoxylin, and available blocks were examined by direct immunofluoresence for Rickettsia rickettsii. Cases and controls matched for age and sex were randomized and examined blindly for pathologic changes. In addition, morphometric measurements of mean alveolar septal thickness were made in each case. The histopathologic findings include (1) diffuse interstitial mononuclear (lymphocyte and macrophage) inflammatory infiltrate in 15/16 cases of RMSF (5/10 controls), (2) pulmonary edema and intraalveolar hemorrhage in 11/16 cases of RMSF (2/10 controls), and (3) vasculitis of small pulmonary venules and arterioles in 5/16 RMSF cases (0/10 controls). Rickettsia rickettsii were identified in 4/8 RMSF cases by direct fluorescent antibody technique. Although pulmonary disease is not always clinically apparent in children with RMSF, involvement of the pulmonary microcirculation is a frequent event in fatal cases and may contribute to the development of non-cardiogenic pulmonary edema.
Insights
Rocky Mountain spotted fever (RMSF) frequently causes lung pathology in children, even without obvious respiratory symptoms. Histopathology reveals inflammation, edema, and vasculitis, indicating microcirculation involvement in fatal cases.
Area of Science:
- Pathology
- Infectious Diseases
- Pediatrics
Background:
- Rocky Mountain spotted fever (RMSF) is a severe tick-borne illness.
- Pulmonary involvement in pediatric RMSF is not always clinically apparent.
- Understanding lung pathology is crucial for managing severe RMSF cases.
Purpose of the Study:
- To investigate the histopathologic changes in the lungs of children who died from RMSF.
- To correlate clinical presentation with lung pathology in pediatric RMSF.
- To identify the presence of Rickettsia rickettsii in affected lung tissues.
Main Methods:
- Histopathologic examination of lung tissues from RMSF cases and age/sex-matched controls.
- Staining techniques including hematoxylin and eosin, phosphotungstic acid-hematoxylin.
- Direct immunofluorescence for Rickettsia rickettsii and morphometric analysis of alveolar septal thickness.
Main Results:
- 15 of 16 fatal RMSF cases showed significant lung histopathology.
- Common findings included interstitial inflammation (15/16), pulmonary edema/hemorrhage (11/16), and vasculitis (5/16).
- Rickettsia rickettsii was detected in 4/8 RMSF cases via immunofluorescence.
Conclusions:
- Pulmonary microcirculation involvement is frequent in fatal pediatric RMSF.
- Histopathologic lung changes can occur despite infrequent respiratory symptoms.
- RMSF-related pulmonary vasculitis may contribute to non-cardiogenic pulmonary edema.