Aristolochic acid

Aristolochic acid is an herb used in many varieties of Chinese herbs and health supplements. Interestingly, it also can cause a severe form of interstitial nephritis which has been known by several names, most notably "Chinese herb nephropathy" (all patients with unexplained renal failure should be queried as to any over-the-counter supplements) as well as "Balkan nephropathy" (named for an epidemiologic clustering of interstitial nephritis in Eastern Europe). Patients with aristolochic acid toxicity are also prone to developing malignancies of the urinary tract (e.g. bladder cancer).