In acute interstitial nephritis, the tubular damage leads to renal tubular dysfunction, with or without renal failure. Regardless of the severity of the damage to the tubular epithelium, the renal dysfunction is generally reversible, possibly reflecting the regenerative capacity of tubules with preserved basement membrane. Conversely, chronic tubulointerstitial nephritis is characterized by interstitial scarring, fibrosis, and tubule atrophy, resulting in progressive chronic renal insufficiency.[1, 2]
The principal mechanism in acute tubulointerstitial nephritis is hypersensitivity reaction to drugs such as penicillins, nonsteroidal anti-inflammatory drugs (NSAIDs), and sulfa drugs. Another mechanism is acute cellular injury caused by infection, viral or bacterial, often associated with obstruction or reflux. The kidney is remarkably resistant to structural damage in bacterial infections, and, in the absence of obstruction, damage from bacterial infection in the kidney parenchyma is extremely unlikely to occur.
Studies have revealed transforming growth factor–beta (TGF-β) as a major participant in fibrogenesis. TGF-β favors accumulation of collagen and noncollagen basement membrane components by direct stimulation of production and by inhibiting matrix degradation enzymes such as collagenases and metalloproteinases. Activation of nuclear transcription factors, such as nuclear factor kappa B (NFκB) in injured kidney cells,[3] with consequent transcription and release of proinflammatory cytokines into the interstitium, appears to be a major mechanism of chronic tubulointerstitial inflammation accompanying proteinuric kidney diseases.