Aetiology of Balkan nephropathy: a reappraisal after 30 years.

Balkan nephropathy (BN) has been a complete aetiological puzzle for many years. Intense research produced many controversial results, but also helped some clues to be traced. Thus, it became rather obvious that the disease is caused by environmental factors (though it may be, to some extent, genetically controlled). Among live agents, slow viruses are the only (and theoretically very attractive) possible cause of both BN and urothelial tumours, which occur frequently in BN endemic areas. Apart from occasional visualization of virus-like particles, other evidence supporting this hypothesis has been lacking. The role biological products, particularly fungal toxins, needs to be further defined. An excess of any heavy metal or radioactive substance as a cause of BN is very unlikely indeed; however, a deficiency of a bio-essential element could not be ruled out. Many epidemiological data indicate that water might be a transmitter of the agent(s). A wide range of ions and minerals have been incriminated, but up to now most of the studies have provided negative or inconclusive results. Organic compounds in well water have never been sufficiently considered. Another ignored area are unstable and, particularly, photosensitive substances. Fertilizers, pesticides, analgesics, local herbs and teas have no causal relation to BN.