Appenzeller et al. (1980) described 2 sisters and a brother with this combination of abnormalities, which appears to be unique. Xenografts into immunologically paralyzed mice showed that the Schwann cells from the patient could myelinate regenerating mouse nerves. Thus, the defect presumably resides in the axon.
Appenzeller, O., Kornfeld, M., Atkinson, R. Pure axonal neuropathy: nerve xenografts and clinicopathological study of a family with peripheral neuropathy, hereditary ataxia, focal necrotizing encephalopathy, and spongy degeneration of brain. Ann. Neurol. 7: 251-261, 1980. [PubMed: 6252824] [Full Text: https://doi.org/10.1002/ana.410070308]