Peripheral nerve in type III glycogenosis: selective involvement of unmyelinated fiber Schwann cells.

Electron microscopy of intramuscular nerves in biopsy material from a child with glycogenosis type III showed massive glycogen accumulation in the Schwann cells of unmyelinated nerve fibers. Other cells, including Schwann cells of myelinated fibers, perineurial cells, endoneurial fibroblasts, endothelial cells, and pericytes, were not similarly affected.