Hereditary metabolic neuropathies.

Hereditary metabolic neuropathies (HMN) are marked by inherited enzyme or other metabolic defects. They comprise lysosomal, mitochondrial, and peroxisomal diseases, i.e. multiorgan, single-organelle system disorders, vitamin E deficiency, porphyrias, and Tangier disease. In addition to non-specific morphological pathology such as demyelinating or axonal lesions certain groups of HMN are marked by disease-specific inclusions only precisely elucidated with the electron microscope, e.g. lysosomal disorders, vitamin E deficiency, and Tangier disease. The lack of clinical and/or electrophysiological abnormalities in some of the HMN, the predominant involvement of the CNS in others and the occurrence of certain HMN in very young children have often delayed systematic investigations of the PNS in HMN and thus also procrastinated knowledge of the morphological and nosological HMN spectrum.