Ultrastructural defects of the glomerular basement membranes associated with primary glomerular nephropathies.

It is generally accepted that a glomerular basement membrane (GBM) thinner than 200 nm should be considered below normal. When this abnormality has a global and diffuse distribution, the associated clinical condition is a benign familial hematuria related to mutations of the COL4A4/COL4A3 genes, or an Alport syndrome. More often the GBM defects display a focal and segmental pattern, too small to express a thin glomerular basement membrane disease. The aim of this study is to emphasize statistical data concerning the pathogenic link between the renal glomerular diseases and the preexisting thin and very thin GBM. A series of 487 renal biopsies from adult patients has been thoroughly investigated both for nephropathologic diagnosis and the GBM ultrastructure. It has been statistically concluded that there is a close coexistence of primary glomerulonephritis and thin glomerular basement membranes with the role of a predisposing condition for immune complex deposition.