Figure 34

Thin basement membrane nephropathy. Glomeruli with abnormally thin basement membranes may be a manifestation of benign familial hematuria. Glomeruli with thin basement membranes many also occur in persons who do not have a family history of renal disease but who have hematuria, low-grade proteinuria, or both. Although the ultrastructural abnormalities have some similarities in common with the capillary basement membranes of Alport's syndrome, these two glomerulopathies are not directly related. Clinically, persistent microscopic hematuria or occasional episodic gross hematuria are important features. Nonrenal abnormalities are absent. On light microscopy, the glomeruli are normal; no deposits are seen on immunofluorescence. Here, the electron microscopic abnormalities are diagnostic; all or virtually all glomerular basement membranes are markedly thin (<200 nm in adults) without other features such as splitting, layering, or abnormal subepithelial contours.

of the enzyme a-galactosidase with accumulation of sphingolipids in many cells. In the kidney, accumulation of sphingolipids especially affects glomerular visceral epithelial cells. Deposition of sphin-golipids in the vascular tree may lead to premature coronary artery occlusion (angina or myocardial infarction) or cerebrovascular insufficiency (stroke). Involvement of nerves leads to painful acropares-thesias and decreased perspiration (anhidrosis). The most common renal manifestation is that of proteinuria with progressive renal insufficiency. On light microscopy, the morphologic abnormalities of the glomeruli primarily consist of enlargement of visceral epithelial cells and accumulation of multiple uniform small vacuoles in the cytoplasm (arrow in Panel A). Ultrastructurally, the inclusions are those of whorled concentric layers appearing as "zebra bodies" or myeloid bodies representing sphingolipids (B). These structures also may be observed in mesangial and endothelial cells and in arterial and arteriolar smooth muscle cells and tubular epithelia. At considerably higher magnification, the inclusions are observed to consist of multiple concentric alternating clear and dark layers, with a periodicity ranging from 3.9 to 9.8 nm. This fine structural appearance (best appreciated at the arrow) is characteristic of stored glycolipids (C).

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