Polyarteritis nodosa and peripheral neuropathy. Ultrastructural study of 13 cases.

Peripheral nerves from 13 patients suffering from polyarteritis nodosa with multiple mononeuropathy were studied by light and electron microscopy. In the majority of cases, the vascular lesions were associated with Wallerian-like degeneration. Myelinated fibers presenting a normal axon with a disproportionately thin myelin sheath were less numerous. Unusual abnormalities consisted of swollen axons with an accumulation of organelles. Unmyelinated fibers were also damaged. A quantitative estimation of myelinated fibers loss did not show any selective vulnerability of either the large or the small diameter group.