Peripheral nerve changes in porphyric neuropathy: Findings in a sural nerve biopsy

Summary The changes in a sural nerve biopsy of a patient with porphyric neuropathy were studied by light and electron microscopy. Linear arrays of myelin ovoids constituted the most common abnormality in whole mounts of teased-fiber preparations. Round or irregular formations of variable osmiophilia were the most frequent finding in thick-section preparations examined by phase contrast microscopy. Lamellar whorls represented the most prevalent lesion in thinsections studied under the electron microscope. In addition, along the teased fibers, segmental demyelination was definitely detected, although rarely; in thick sections, the true extent of the nerve fiber loss was fully appreciated; in thin sections, a variety of axon and myelin changes of a distinct character were discovered. The studies demonstrate that in peripheral nerves of porphyric neuropathy, axonand myelin changes generally run together and proceed pari passu in the same segment of nerve fiber. Furthermore, among the pathogenetic mechanisms invoked to account for the neuropathic changes none are favored to the exclusion of others by these studies. Therefore, a primary axonaland myelinic disorder on the basis of a deranged porphyrin metabolism is as good a possibility as any hitherto advanced explanation of the pathogenesis of the neuropathic changes. The secondary lesions of Wallerian degeneration and segmental demylination may simple be grafted upon the primary lesions evoked by the metabolic abnormality.