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What is Balkan endemic nephropathy and explain in detail?
Balkan endemic nephropathy (BEN) is a form of interstitial nephritis causing kidney failure. It was first identified in the 1920s among several small, discrete communities along the Danube River and its major tributaries, in the modern countries of Croatia, Bosnia and Herzegovina, Serbia, Romania, and Bulgaria. It is caused by small long-term doses of aristolochic acid in the diet. The disease primarily affects people 30 to 60 years of age. Doses of the toxin are usually low and people moving to endemic areas typically develop the condition only when they have lived there for 10–20 years. People taking higher doses of aristolochic acid (as Chinese herbal supplements) have developed kidney failure after shorter durations of exposure.

Signs and symptoms
The patients are distinguished from those suffering from other causes of end-stage renal disease by showing an absence of high blood pressure, xanthochromia of palms and soles (Tanchevs sign), early hypochromic anemia, absence of proteinuria, and slow progression of kidney failure.  There is no specific therapy; BEN causes end-stage renal disease, for which the only effective treatments are dialysis or a kidney transplant. In endemic areas BEN is responsible for up to 70% of end-stage renal disease. At least 25,000 individuals are known to have this form of the disease.Patients with BEN have a greatly increased rate of transitional cell carcinoma of the upper urothelial tract, (the renal pelvis and ureters). (In populations without BEN, most urothelial cancer occurs in the bladder. )

Causes
Dietary exposure to aristolochic acid is the cause of BEN and its attendant transitional cell cancers