A patient with antineutrophil cytoplasmic antibody–negative pulmonary capillaritis and circulating primed neutrophils

We describe an antineutrophil cytoplasmic antibody–negative patient with capillaritis, acute respiratory failure, and primed neutrophils circulating systemically. Thoracoscopic lung biopsy showed capillary destruction, with neutrophils infiltrating the lung interstitium and air spaces but no alveolar damage or hemorrhage. We suggest that this atypical, limited form of pulmonary injury may occur when circulating neutrophils are primed, but, in the absence of an activating factor, not fully activated.