Electron microscopy for measurement of glomerular basement membrane width in children with benign familial hematuria.

Glomerular basement membrane (GBM) width was measured in 13 children with benign familial hematuria (BFH) and in 13 controls (6 children and 7 adults), using a standardized procedure and examining 3 glomeruli in each case. GBM widths were evaluated by comparing arithmetic means and considering the frequency of segments with a thickness less than 150 and 200 nm. With the former method, only 6 children with BFH fell below the normal values, while with the latter, 9 out of 13 were below the normal range. When BFH is suspected, it appears that GBM width is best evaluated by considering only the thinner segments, because the arithmetic mean can be influenced by the presence of thick segments and therefore has less diagnostic value.