[Tubulointerstitial nephritis]

A concept of the pathogenesis of tubular interstitial nephritis (TIN) is presented, based on histologic, immunohistologic and electromicroscopic investigations on 61 patients with glomerulonephritis, lupus erythematodes and rheumatoid arthritis. The pathogenic model is a hypersensitivity reaction which leads to alterations in the tubular basement membrane (TBM) and results in changes in the TBM and secondary damage to stroma, vessels and tubular cells. The findings change depending on the stage, reflecting the transition from an acute to a chronic process. In acute TIN which is generally a drug allergy, the dominant characteristic of the inflammatory process allows the reaction to be categorized in edematous (72%), cellular (23%) and tubular necrotic (5%) types. The cellular types show 4 subdivisions: plasma cellular, eosinophil-granulocytic, lymphohistiocytic and granulomatous. Chronic TIN is in particular characterized through the destruction of the TBM, dystrophy and atrophy of the tubules as well as their degeneration, lymphohistiocytic infiltrates and sclerotic stroma reactions. A distinction is made between cellular destructive and atrophic-sclerotic types. At view of the etiology and pathogenesis a distinction should be made between an infectious and non-infectious TIN and further by the character of the immunoreaction, into a primary and secondary form. If there glomerular changes are present and there is evidence of an immune phenomenon in the glomeruli and TBM we recommend the use of the term glomerulo-tubulo-interstitial nephritis.