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FIG 4. A and B, LM and EM of the sural nerve specimen (Toluidin blue stain, semi-thin section) in a patient with the congenital hypomyelinating form of DSD (case 8).
On LM (A), a decreased number of myelinated fibers with peri- and epineural connective tissue hypertrophy is noted (arrow). Very few residual thinly myelinated fibers (open black arrow) are observed. Note the absence of onion bulbs and connective tissue hypertrophy (thick black arrows) with fibroblasts (black arrowhead). On EM (B), complete absence of myelin sheaths around axons is seen. A Schwann cell nucleus is indicated by the arrow.
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