Lung biopsy in the diagnosis of pediatric ANCA-associated vasculitis

To investigate pulmonary histopathologic features in a cohort of pediatric patients with anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) who underwent a lung biopsy as part of their evaluation. We report the safety and the findings of lung biopsies in this population.

After IRB approval, we performed a retrospective chart review of all patients <18 years of age presenting to our institution with a diagnosis of pediatric AAV (pAAV) who underwent lung biopsy. We reviewed histopathologic features, serologies, the timing of biopsy, and complications.

Fourteen patients met inclusion criteria, nine patients with microscopic polyangiitis (MPA), and five patients with granulomatosis with polyangiitis (GPA). All patients had positive ANCA serology. 13/14 patients required admission on initial presentation for respiratory symptoms; 11/13 required respiratory support. The indication for biopsy was confirmation of diagnosis before initiating therapy in 11 patients (78%), part of the infectious evaluation in two (14%), and part of interstitial lung disease evaluation in one (7%). 11/14 (78%) biopsies had findings consistent with AAV diagnosis: 6/9 (67%) of the MPA patients compared with 5/5 (100%) of the GPA patients. The most common findings on histopathology were vascular inflammation and signs of alveolar hemorrhage. The only reported complication after lung biopsy was pneumothorax in four patients (28%).

Lung biopsy had a higher diagnostic yield in GPA compared with MPA patients. In our cohort, a diagnosis of AAV could be made with clinical features and positive serology but was confirmed by lung histopathology in the majority of cases. Obtaining a lung biopsy for diagnostic purposes in pAAV should be reserved for uncertain cases where the diagnosis cannot be confirmed clinically and with serology.