Rheumatoid Lung Disease, Organizing Pneumonia, and the Pathology of Pulmonary Drug Toxicity

Abstract

We report histologic findings on open lung biopsies from 2 patients with acute lung symptoms and a long-standing history of rheumatoid arthritis. The findings in 1 patient, who had been treated with methotrexate, include organizing pneumonia and rheumatoid (necrotic) nodules superimposed on underlying interstitial fibrosis with focal honeycombing, consistent with rheumatoid lung disease. The clinical differential diagnosis in this patient includes drug (methotrexate) toxicity. The second patient’s biopsy results had features of capillaritis with superimposed diffuse alveolar damage—2 patterns of acute lung injury that occur in rheumatologic disorders and have a relatively poor prognosis. Although organizing pneumonia is often considered characteristic of rheumatoid lung disease, a variety of other patterns are more common. The clinical differential diagnosis of rheumatoid lung includes infection and drug toxicity, especially when it is in an acute stage.