Unusual ultrastructural features in a case of acute diffuse proliferative glomerulonephritis

A case consistent with recurrent acute poststreptococcal glomerulonephritis but with atypical features is described. Light microscopy revealed a diffuse proliferative glomerulonephritis. A spectrum of ultrastructural features, from the typical "humpy bumpy" subepithelial deposits to the apparent disappearance of the deposits within the epithelial cells, is presented. An unusual piling up of basement membrane material around the deposits is described, together with some areas showing an appearance reminiscent of membranous glomerulopathy. Resorption of the dense deposits within epithelial cells is suggested and a hypothesis advanced that the basement membrane reaction may indicate an incipient chronic immune complex lesion.