Figure 634

A, Interstitial foam cells in Alport's syndrome. B, Late phase Alport's syndrome showing chronic TIN and glomerular changes in a patient with massive proteinuria. Tubulointerstitial lesions are a prominent component of the renal pathology of a variety of hereditary diseases of the kidney, such as medullary cystic disease, familial juvenile nephronophthisis, medullary sponge kidney, and polycystic kidney disease. The primary disorder of these conditions is a tubular defect that results in the cystic dilation of the affected segment in some patients. Altered tubular basement membrane composition and in a geographic area bordering the Danube River as it traverses Romania, Bulgaria, and the former Yugoslavia. The cause of Balkan nephropathy is unknown; however, it has been attributed to genetic factors, heavy metals, trace elements, and infectious agents. The disease evolves in emigrants from endemic regions, suggesting a role for inheritance or the perpetuation of injury sustained before emigration.

Initially thought to be restricted to Scandinavian countries, and thus termed Scandinavian acute hemorrhagic interstitial nephritis, Nephropathia epidemica has been shown to have a more universal occurrence. It therefore has been more appropriately renamed hem-orrhagic fever with renal syndrome. As a rule the disease presents as a reversible acute tubulointerstitial nephritis but can progress to a chronic form. It is caused by a rodent-transmitted virus of the Hantavirus genus of the Bunyaviridae family, the so-called Hantaan virus. Humans appear to be infected by respiratory aerosols contaminated by rodent excreta. Antibodies to the virus are detected in the serum, and viruslike structures have been demonstrated in the kidneys of persons infected with the virus.

Tubulointerstitial nephropathy caused by viral infection also has been reported in polyomavirus, cytomegalovirus, herpes simplex virus, human immunodeficiency virus, infectious mononucleosis, and Epstein-Barr virus.

associated epithelial cell proliferation account for cyst formation. It is the continuous growth of cysts and their progressive dilation that cause pressure-induced ischemic injury, with consequent TIN of the adjacent renal parenchyma.

Tubulointerstitial lesions also are a salient feature of inherited diseases of the glomerular basement membrane. Notable among them are those of hereditary nephritis or Alport's syndrome, in which a mutation in the encoding gene localized to the X chromosome results in a defect in the a-5 chain of type IV collagen.

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