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Peripheral nerve biopsies (PNB) from four children suffering from subacute or chronic inflammatory demyelinating polyneuropathy were studied by electron microscopy. Remyelinating features with onion bulb formations, inflammatory cell infiltrates and active demyelinating lesions were strongly suggestive of the disease. In the first case, a second PNB, performed after 7 months of severe subacute course, showed a striking evolution of the lesions. In the second case and in spite of severe neurological symptoms, the PNB was almost normal, suggesting that inflammatory lesions were mainly located in the proximal parts of the nerve. No signs of active demyelination could be seen in the third case but onion bulb formations and inflammatory cell infiltrates were present. In the fourth case, characteristic lesions of active demyelination were associated with a history of familial polyneuropathy; this association suggests an autoimmune process in certain kindreds with hereditary motor and sensory neuropathy.

Four cases of early infantile polyneuropathy with defective myelination are reported. The peripheral nerve was studied by light and electron microscopy; different morphological characteristics have been noticed in these patients. Case 1 presented aspects of defective myelination with atypical “onion bulb” formation composed of multiple layers of basement membrane. In case 2, defective myelination and atypical “onion bulb” formation were associated with aberrant hypermyelination. Cases 3 and 4 were brothers, who presented axonal damage and atypical “onion bulb” formation.

Inflammatory demyelinating polyradiculoneuropathies exhibit well-known ultrastructural lesions of the peripheral nerve, both in acute cases, i.e., Guillain-Barré syndrome, and in relapsing, subacute and chronic cases. We present a case of relapsing inflammatory demyelinating polyradiculoneuropathy in a diabetic patient with a biopsy exhibiting these lesions, as well as a widening of the outermost myelin lamellae in some fibers. Such associated lesions are classic in experimental inflammatory demyelinating polyradiculoneuropathies, but have not been reported in human pathology.

Peripheral nerve biopsies from two patients with chronic sensorimotor neuropathy were studied. The first case was a non-Hodgkin malignant lymphoma and did not show any dysglobulinemia. The second case had a benign monoclonal gammopathy IgG, Lambda type. Direct immunofluorescence showed no deposits in the first case and slight deposits of anti IgG sera on a few myelinated fibers in the second case. There were numerous fibers showing uncompacted myelin lamellae, 7% in the first case and 4% in the second case. Some of these fibers had axons containing more tubules than filaments. The very few cases reported on neuropathies showing that uncompacted myelin lamellae were frequently associated with dysglobulinemic neuropathy. However, this ultrastructural abnormality of the myelin sheath can be observed without any dysglobulinemia.

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.

The peripheral nerve was taken from 25 diabetic patients with arteritis just before or after amputation of a leg. The ultrastructural study of myelinated fibers showed several alterations. Loss of fibers varied greatly from case to case. This was accompanied in some cases by hypertrophy of the Schwann cells around demyelinated fibers as has been observed in some ordinary diabetic neuropathies. Unusual abnormalities consisted of particular axonal degeneration and evidence of aberrant remyelination. This axonal injury was peculiar because of the accumulation of organelles which tended to transform some of the fibers into enlarged axons. Such a lesion might correspond to a hypoxic axonopathy.

We report the ultrastructural findings in superficial peroneal nerve biopsies in two patients, one with idiopathic sensory neuropathy and the other with the Guillain-Barré syndrome and Hodgkin's disease. In addition to demyelination, there was an intense proliferation of microfilaments within numerous vesicles of the endoplasmic reticulum of a great number of myelinated Schwann cells. This abnormality does not appear to have been previously reported in the literature. The mechanisms responsible for this finding are unknown.