Collagenofibrotic Glomerulopathy

FIGURE 2-32 (see Color Plate)

Collagenofibrotic glomerulopathy (collagen III glomerulopathy). The collagens normally found in glomerular basement membranes and the mesangial matrix are of types IV (which is dominant) and V. In collagenofibrotic glomerulopathy, accumulation of type III collagen occurs largely in capillary walls in a suben-dothelial location. It is likely that this disease is hereditary; however, because it is very rare, precise information regarding transmission is not known. Collagenofibrotic glomerulopathy originally was thought to be a variant of nail-patella syndrome. Current evidence suggests little relationship exists between the two disorders. Patients with collagen III glomerulopathy often

exhibit proteinuria and mild progressive renal insufficiency. For reasons that are not clear, hemolytic-uremic syndrome has evolved in a small number of pediatric patients. A, On light microscopy the capillary walls are thickened and mesangial regions widened by pale staining material. These features are in sharp contrast to the normal staining of the capillary basement membranes, as evidenced by the positive period acid-Schiff reaction. With this stain, collagen type III is not stained and therefore is much paler. Amyloid stains (Congo red) are negative. B, On electron microscopy, banded collagen fibrils are evident in the subendothelial aspect of the capillary wall.

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