Myeloperoxidase Anti-Neutrophil Cytoplasmic Antibody-Positive Interstitial Pneumonia Associated with Granulomatosis with Polyangiitis Diagnosed by Surgical Lung Biopsy

Abstract

Granulomatosis with polyangiitis (GPA) is a rare systemic vasculitis that often involves the lung. However, interstitial pneumonia (IP) is rarely seen in GPA patients. We herein report 3 cases of IP associated with GPA diagnosed by surgical lung biopsy. High-resolution CT showed uniform subpleural reticular opacity with traction bronchiectasis. Biopsies from all 3 patients revealed neutrophilic capillaritis, microabscesses with giant cells, and coexisting histological findings of usual IP pattern or fibrosing nonspecific IP pattern. All 3 patients had elevated levels of serum myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA), but not proteinase 3-ANCA. We diagnosed GPA and treated with corticosteroid and cyclophosphamide. Follow-up CT showed improvement of the lesions in all patients. Surgical lung biopsy specimens which revealed GPA enabled us to conduct the most suitable therapy. This report indicates the importance of surgical lung biopsy for differentiating idiopathic IPs from GPA-associated IP and suggests a relationship between MPO-ANCA and IP in GPA.

EULAR recommendations for the management of ANCA-associated vasculitis: 2022 update

“…47 48 In patients with pulmonary lesions that cannot be clearly attributed to active AAV, thoracoscopic or open lung biopsies can be considered. [49][50][51] When obtaining or interpreting a biopsy is challenging, surrogate markers can support a clinical diagnosis of AAV that is based on a typical clinical presentation and positive proteinase 3 (PR3)-ANCA or myeloperoxidase (MPO)-ANCA serology. 52 Such surrogate parameters can be either clinical (such as mononeuritis multiplex confirmed by electrophysiological studies), laboratory data (such as red blood cell casts in the urine suggestive of glomerulonephritis) or findings on imaging.…”

Myeloperoxidase and associated lung disease: Review of the latest developments

“…The evidence for immunosuppression is variable in this small cohort of non‐AAV MPO‐ANCA ILD patients. Biopsies of non‐AAV MPO‐ANCA‐positive patients with UIP have more inflammation than MPO‐ANCA‐negative patients with UIP, 74 suggesting that immunosuppression may be beneficial.…”

Enfermedad pulmonar intersticial asociada a vasculitis sistémica ANCA positiva. Monografía 2018

“…Se le realizó biopsia pulmonar a cielo abierto a los 3 pacientes, las cuales evidenciaron capilaritis, microabscesos con células gigantes y coexistencia de patrón UIP con patrón NSIP. Todos los pacientes presentaban ANCA MPO positivo, pero no PR3 45 .…”