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Necrotizing alveolar capillaritis in autopsy cases of microscopic polyangiitis. Incidence, histopathogenesis, and
Objectives:
To determine the incidence of necrotizing alveolar capillaritis, to elucidate its histopathogenesis and the most reliable histopathologic features for its detection, and to explore its relationship with systemic vasculitis in microscopic polyangiitis.
Methods:
Twenty-five autopsy cases of microscopic polyangiitis were examined. Double staining with periodic acid-silver methenamine and trichrome was used.
Results:
Periodic acid-silver methenamine and trichrome staining proved to be a useful and convenient method for the detection of necrotizing alveolar capillaritis. Capillaritis was detected in 10 (40%) of the 25 cases studied. Of 18 cases that exhibited the early degenerative stage of systemic vasculitis, capillaritis was seen in 10 (56%). Fibrinoid necrosis of the alveolar wall was the most reliable histopathologic feature for detecting necrotizing alveolar capillaritis in microscopic polyangiitis. The early stage of capillaritis displayed very little neutrophil exudation, and conspicuous accumulation of neutrophils developed after fibrinoid necrosis. Statistical analysis revealed that alveolar capillaritis had a statistically significant correlation (P < .05) with necrotizing vasculitis of the pulmonary circulatory system. Capillaritis tended to occur when systemic vasculitis of microscopic polyangiitis was in its early degenerative stage.
Conclusion:
Necrotizing alveolar capillaritis was detected in about half of the microscopic polyangiitis autopsy cases that exhibited the early degenerative stage of systemic vasculitis, and results based on earlier reports of clinical observations may have been too conservative.
Insights
Necrotizing alveolar capillaritis occurs in 40% of microscopic polyangiitis autopsy cases. Fibrinoid necrosis of the alveolar wall is a key indicator, often appearing in the early stages of systemic vasculitis.
Area of Science:
- Pulmonary Pathology
- Rheumatology
- Histopathology
Background:
- Microscopic polyangiitis (MPA) is a systemic vasculitis that can affect the lungs.
- Necrotizing alveolar capillaritis is a pulmonary manifestation of MPA.
- Accurate histopathologic diagnosis is crucial for understanding MPA's pulmonary involvement.
Purpose of the Study:
- To determine the incidence of necrotizing alveolar capillaritis in MPA.
- To elucidate its histopathogenesis and reliable diagnostic features.
- To explore its relationship with systemic vasculitis in MPA.
Main Methods:
- Autopsy examination of 25 MPA cases.
- Utilized double staining with periodic acid-silver methenamine and trichrome.
- Focused on identifying histopathologic features of alveolar capillaritis.
Main Results:
- Necrotizing alveolar capillaritis detected in 10 (40%) of 25 MPA cases.
- Fibrinoid necrosis of the alveolar wall identified as the most reliable feature.
- Capillaritis correlated significantly with necrotizing vasculitis and often occurred in early MPA stages.
Conclusions:
- Necrotizing alveolar capillaritis is a significant finding in MPA, present in about half of cases with early systemic vasculitis.
- Histopathologic findings suggest earlier reports may have underestimated its incidence.
- Periodic acid-silver methenamine and trichrome staining is an effective diagnostic method.