Pulmonary Capillaritis: The Breakdown of the Histologic Features

Abstract

Abstract Introduction/Objective Capillary inflammation (capillaritis) is rarely the primary pathologic cause of pulmonary hemorrhage. It may coexist with vasculitis. The aim of this study is to investigate the specificity of five histologic features of pulmonary capillaritis previously described by Mark and Ramirez (discussed below). They are usually treated with corticosteroids and cyclophosphamide or azathioprine. Methods A retrospective review of patients with a pathologic diagnosis of capillaritis in open lung biopsies was done. The diagnosis was confirmed by two expert pulmonary pathologists. The slides were reviewed and compared to a control group, who also underwent open lung biopsies for clinical suggestion of pulmonary hemorrhage and no pathologic diagnosis of capillaritis. Cases with malignant neoplasms, large and medium size vasculitis syndromes, and diffuse alveolar damage (DAD) were excluded. The five pathologic features of capillaritis were evaluated and scored as negative (0), focal (1+) and moderate to diffuse (2+) in both groups. Results Five cases of pulmonary capillaritis and five cases in control group were identified. The etiology of pulmonary capillaritis in the five identified cases included autoimmune diseases, pulmonary hypertension, non-specific interstitial pneumonia, and idiopathic capillaritis. The average score for the morphologic features of capillaritis versus the control group were as follows: Interstitial erythrocytes and/or hemosiderin (2+ vs 2+), fibrinoid necrosis of capillary walls (2+vs 0), intraalveolar septal capillary occlusion by fibrin thrombi (1+ vs 0), neutrophils and nuclear dust in the interstitium, in the fibrin, and in the adjacent alveolar spaces (2+ vs 1+), and fibrin clots attached to interalveolar septa in a sessile manner (2+ vs 1+). Conclusion In this small study, we can conclude that fibrinous necrosis is the most specific finding for pulmonary capillaritis while interstitial erythrocytes and/or hemosiderin is least specific. Therefore, in the presence of fibrinous necrosis; in addition to other supporting features; a pathologist is more inclined to communicate a diagnosis of pulmonary capillaritis to the clinicians.