Idiopathic retroperitoneal fibrosis: a systemic connective tissue disease?

Renal histology of a patient with idiopathic retroperitoneal fibrosis demonstrated a proliferative crescentic glomerulonephritis with intramembranous electron-dense deposits. These findings were interpreted as being consistent with an immune complex glomerulonephritis. Serologic studies revealed a positive antismooth muscle antibody titer of 1:80 and a weakly positive antinuclear antibody titer of 1:40. No distinct systemic disease was identified. While fibrosis of the retroperitoneum can occur in association with a number of distinct pathologic conditions and pharmacologic agents, the mechanism responsible for the development of the idiopathic variety of retroperitoneal fibrosis remains unclear. Our observation of an immune complex glomerulonephritis and the cumulative data on idiopathic retroperitoneal fibrosis are consistent with the concept that the fibrosis may be a local expression of an immunologically mediated systemic disease.