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[Two cases of microscopic polyangitis with preceding interstitial pneumonia diagnosed by surgical lung biopsy]
Hiroyuki Kamiya1, Soichiro Ikushima, Rie Ishikawa
1Division of Respiratory Medicine, Japanese Red Cross Medical Center.
Abstract:
We encountered 2 cases of microscopic polyangitis (MPA) with preceding interstitial pneumonia. The patients were elderly men, and radiological findings showed a UIP pattern in both cases. Furthermore, ANCA-associated vasculitis had been suspected since the first admission in case 1, because MPO-ANCA tests were positive, and the surgical lung biopsy revealed vasculitis in a honeycomb lesion. A diagnosis of idiopathic pulmonary fibrosis was made in case 2 because no findings of vasculitis were pathologically confirmed, and MPO-ANCA was not examined. Both patients were followed up without any treatment, but steroid therapy with immunosuppressants was initiated after a diagnosis of MPA was made from a renal failure complication. Remission continued in case 1, but patient 2 died due to a pulmonary hemorrhage complication, despite some temporary improvements. An autopsy revealed massive alveolar hemorrhage and neutrophil infiltration in the alveolar walls that suggested pulmonary capillaritis, in spite of the absence of pathological evidence, which was not detected in the honeycomb lesions. These 2 cases indicate that MPO-ANCA should be examined in the follow-up of chronic interstitial pneumonia. Furthermore, it should be assumed that the size of involved blood vessels, their distribution and the timing of occurrence may be different in individual case of ANCA-associated interstitial pneumonia.
Insights
Microscopic polyangitis (MPA) can precede interstitial pneumonia, particularly in elderly men with UIP patterns. Testing for myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA) is crucial for diagnosing ANCA-associated vasculitis in such cases.
Area of Science:
- Pulmonology
- Rheumatology
- Nephrology
Background:
- Microscopic polyangitis (MPA) is a rare systemic vasculitis often associated with interstitial pneumonia.
- Idiopathic pulmonary fibrosis (IPF) and ANCA-associated vasculitis (AAV) can present with overlapping radiological and pathological features.
Observation:
- Two elderly male patients with preceding interstitial pneumonia exhibiting a usual interstitial pneumonia (UIP) pattern were diagnosed with MPA.
- One patient had positive MPO-ANCA and vasculitis confirmed on lung biopsy, while the other initially received an IPF diagnosis due to lack of pathological vasculitis evidence and unexamined MPO-ANCA.
- Both patients were treated with immunosuppressants and steroids following MPA diagnosis due to renal complications.
Findings:
- MPA diagnosis was confirmed in both cases, leading to remission in one and fatal pulmonary hemorrhage in the other despite initial improvements.
- Autopsy in the deceased patient revealed pulmonary capillaritis, suggesting ANCA-associated vasculitis despite prior negative findings in honeycomb lesions.
- These cases highlight the diagnostic challenges and potential for delayed recognition of MPA in patients with interstitial lung disease.
Implications:
- Myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA) testing should be considered in the follow-up of patients with chronic interstitial pneumonia.
- The presentation of ANCA-associated interstitial pneumonia can vary significantly regarding vessel size, distribution, and timing.
- Early and accurate diagnosis of MPA in patients with interstitial pneumonia is critical for timely treatment and improved outcomes.