Diagnose This (April 22, 2019)

What is this finding and what diagnoses does it imply?

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This is an electron microscopy image showing a high power view of several capillary loops, mesangium and Bowman’s space. The most striking finding here is of diffuse, near complete epithelial foot process effacement with microvillus transformation. This level of epithelial foot process effacement can be seen in several kidney diseases but as no immune complex deposits are present we can exclude immune complex mediated glomerular disease. Additionally, no light chain deposits or fibrils are present so it is unlikely we are dealing with an amyloidosis, fibrillary glomerulopathy, or light chain deposition disease. In a question like this, where isolated, diffuse epithelial foot process effacement is present the question is usually directing you toward a podocytopathy such as minimal change disease or primary focal segmental glomerulosclerosis. In this particular case, the biopsy showed unremarkable glomeruli by light microscopy and a negative immunofluorescence panel and was consistent with minimal change disease.