English: Sural nerve pathology in patients with mutations in SLC52A2. Resin semi-thin sections, stained with methylene blue–azure A and basic fuchsine; ×63 magnification (A and C) and toluidine blue; ×40 magnification (F) and electron microscopy examination (B, D and E) of sural nerve fascicle cross sections in Patient E2 at 2 years of age (A and B), Patient E3 at 4 years of age (C and D), Patient E5 at 4 years of age (E), and Patient A3 at 3 years of age (F) demonstrate a loss of myelinated axons, preferentially of large diameters (8–12 µm). The endoneurium is fibrotic, and there are no inflammatory infiltrates. Numerous redundant Schwannian profiles (Bands of Büngner) are discernible ultrastructurally (B and D, arrows) consistent with the loss of myelinated fibres. Several myelinated fibres in the biopsy of Patient E5 (E) appear vacuolated and slightly enlarged—probably an artefactual change not to be confused with giant axons. Note the striking absence of regeneration clusters in all biopsies. Scale bars: B and D = 5 µm; E = 50 µm.