A diabetic woman underwent an incision of the right big toe for an abscess and developed a typical Guillain-Barré syndrome 48 h later. A biopsy of a peripheral nerve, performed 10 days later, showed modifications usually seen in diabetic patients, as well as the characteristic ultrastructural modifications of the Guillain-Barré syndrome (GBS). Moreover, 22% of myelinated fibers exhibited vesicular disruption of the myelin sheaths. This lesion is rarely encountered on the biopsies of peripheral nerve in GBS and concerns only a few myelinated fibers. Such a prominence of myelinic vesicular disruption and its occurrence in a diabetic patient are discussed.