Misdiagnosing renal amyloidosis as minimal change disease.

Background: Minimal change disease (MCD) accounts for 10-15% of all adult nephrotic syndrome cases and requires normal renal histology by light microscopy and negative immunohistology. Foot process effacement on electron microscopy (EM) is typical. Renal amyloid deposits demonstrate pathognomonic green birefringence when viewed under cross-polarized light after staining tissue with Congo red (CR) and may reveal fibrils on EM.