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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 auto-immune process in certain kindreds with hereditary motor and sensory neuropathy.

As has been shown during the course of experimental allergic neuritis, in the Guillain-Barré syndrome there is an invasion of the myelin sheath in certain fibres by a mononuclear cell, with an intact axon. In a series of 45 cases we have been able to show this feature in 31 cases. In certain cases the cytoplasm prolongation of the invading cell was seen in the myelin sheath, forcing apart two neighbouring layers. In five cases we have furthermore observed the presence of mononuclear cells located either between the myelin and the axon which is deformed, or on the inside of the axon. Such an anomaly was frequent in one recent case and was occasionally found in four other cases.

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.

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.

Inflammatory demyelinating polyradiculoneuropathies exhibit well-known ultrastructural lesions of the peripheral nerve, both in acute cases, i.e., Guillain-Barré syndrome, and in relapsing, sub-acute 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.

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.

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.