Podocytic Infolding Glomerulopathy: Pathological Entity or a Distinct Disease Process

We describe a 32-year-old pregnant female with a very distinctive glomerular morphology. She presented with increasing proteinuria in her third trimester and carried a pre-existing diagnosis of systemic lupus erythematosus (SLE). Renal biopsy showed diffusely thickened capillary loops suggestive of class V membranous lupus nephritis. However the immunofluorescence was negative and on electron microscopy the glomerular basement membrane (GBM) was diffusely thickened containing numerous cytoplasmic processes or projections that appear to extend from the podocytes and the endothelial cells, which in some locations appear to extend across the full thickness of the GBM. This unique morphology has been exclusively described in patients from Japan and labeled as Podocytic Infolding Glomerulopathy (PIG). The clinicopathological significance of podocyte infolding however has not been fully ascertained and it is unclear if PIG is a morphological entity or a distinct glomerular disease.