Alveolar hemorrhage and renal microangiopathy in systemic lupus erythematosus - Immune complex small vascular injury with apoptosis

Context.-Acute alveolar hemorrhage in systemic lupus erythematosus usually occurs as a pulmonary-renal syndrome. In most cases, the lungs show "bland" alveolar hemorrhage with little or no inflammation. Whether this alveolar injury is similar to the better-defined noninflammatory renal lupus vasculo pathy is unresolved. Objectives.-To investigate the relationships and the mechanisms of small va scular injury in the lung and kidney of 2 lupus patients who died of diffus e AH. Methods.-We investigated the relationship of AH to immune complex depositio n in the lungs of 6 patients with systemic lupus erythematosus and correlat ed the findings with glomerular and vascular disease in the kidney. Lung an d kidney were studied by light immunofluorescence, and/or electron microsco py; apoptosis was investigated using in situ nick-end labeling. Results.-The clinical course of 2 patients was complicated by alveolar hemo rrhage, and the lungs of these patients revealed alveolar wall Immune compl ex deposits and bland alveolar hemorrhage. These 2 patients had World Healt h Organization class IV lupus nephritis and renal arterioles involved by a noninflammatory lupus vasculopathy. Apoptosis was identified in the lupus m icroangiopathy and in alveolar walls within areas of alveolar hemorrhage. A lveolar wall immune complex deposits were not found in 4 patients who had a lupus glomerulonephritis but did not have renal lupus vasculopathy. Apopto sis was not seen in renal arterioles or lungs of these 4 cases, except in a reas of diffuse alveolar damage or herpesvirus pneumonia. Conclusions.-Our findings indicate that alveolar hemorrhage in systemic lup us erythematosus, characterized by bland alveolar wall changes, is pathogen etically similar to the lupus microangiopathy of the kidney. In both lung a nd kidney, the pathogenesis of the microvascular injury appears to be relat ed to immune complex deposition and the induction of apoptosis.