This biopsy was performed on a 9-year-old female with no significant past medical history, who presents with nephrotic syndrome. The serum creatinine at the time of the biopsy was 0.7 mg/dl. The UPCR was 9.6 g/g. Serum albumin was 2.1 g/dl. Complement levels and ANA were normal/negative. The biopsy shows glomeruli with minimal mesangial matrix expansion and hypercellularity (Fig 1), in the absence of segmental glomerulosclerosis or proliferative lesions. Immunofluorescence was negative for IgA, IgG, IgM, C3, C1q and kappa and lambda light chains (not shown). Electron microscopy shows widespread blunting, widening and effacement of epithelial foot processes (Fig 2), with no evidence of immune deposits or glomerular basement membrane abnormalities.
These findings are compatible with minimal change disease; however, as only 5 glomeruli were available for light microscopy, additional levels were performed on the paraffin block. Deeper sections show a single glomerulus with segmental glomerulosclerosis limited to the takeoff point of the proximal tubule, associated with endocapillary foam cells and epithelial cell capping (Fig 3). These findings are diagnostic of a primary podocytopathy in the form of focal segmental glomerulosclerosis (FSGS), tip variant. This case highlights the importance of performing additional levels on cases suspicious for a primary podocytopathy with a reduced number of glomeruli and absence of sclerosing lesions.
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