Sural nerve biopsy sections. Small endoneural amyloid deposits are shown in the Congo red staining (A) with a positive transthyretin antibody reaction (B). There is a severe axonal loss with antibodies against neurofilament (C). In the p-phenylenediamine-stained semithin sections, only a few remaining myelinated axons (arrow) can be seen, and acute myelin degeneration (arrowhead) is present (D). Electron microscopic images show denervated Schwann cell bands (arrows) (E) and axonal degeneration with myelin debris (arrow) (F).