Interstitial nephritis in a patient with Legionnaires' disease.

Renal involvement in legionnaires' disease is a well-known, yet incompletely understood, complication. Manifestations of renal involvement include proteinuria, hematuria, pyuria, cylindruria, and azotemia. Previous cases of legionnaires' disease with renal involvement have shown pathophysiologic changes consistent with acute tubulointerstitial nephritis or acute tubular necrosis. A toxic metabolite produced by Legionella pneumophila has been theorized to produce a vasoconstrictive effect on the renal microvasculature, leading to ischemia and renal dysfunction. The case reported here is unique in that the patient presented with interstitial nephritis in the absence of pulmonary signs or symptoms.