Acute interstital nephritis. Acute interstitial nephritis represents 10 to 30% of all biopsy-proven acute kidney injury cases. This disease is characterised by infiltration of renal interstitial tissue by in- flammatory cells, leading to oedema, tubulopathy and subsequent fibrotic lesions. There are multiples causes, such as drug-induced nephropathy (either from direct toxicity or immuno- allergic reaction), infectious diseases, auto-immune processes or malignancy-associated kidney involvement. Extrarenal symptoms are often absent and proteinuria is usually mild with no albuminuria, associated with aseptic leukocyturia. Treatment of this condition frequently requires corticosteroids, together with withdrawal of nephrotoxic drugs, initiation of anti-infectious agents or cytotoxic chemotherapy, depending on the cause of nephropathy.