Reduplication of the glomerular basement membrane. A study of 110 cases.

In 110 cases in which reduplication of the glomerular basement membrane was exhibited, the cellular components and the severity of reduplication were assessed. Sixty-three patients had only endothelial splits; two, only mesangial; and 45, endothelial-mesangial. The most severe splits occurred in transplant rejection and membranoproliferative glomerulonephritis. In cases of transplant rejection endothelial splits were more conspicuous than combined splits, and in membranoproliferative glomerulonephritis the converse was found. We found no evidence of antecedent membranoproliferative glomerulonephritis in any of our cases of transplant rejection, which suggests that the splits observed represented an alteration intrinsic to rejection rather than to recurrent membranoproliferative glomerulonephritis. Previous reports have emphasized the occurrence of mesangial cytoplasm within splits, but the present study demonstrated that reduplication of glomerular basement membrane involves both endothelial and mesangial cells.