Hereditary neuropathy with liability to pressure palsies (HNPP) with progressive deafness and demyelination in the central nervous system
Introduction: Hereditary neuropathy with liability to recurrent pressure-sensitive palsies is rare in childhood. Recurrent painless monofocal palsy triggered by compression of the nerve is the typical presentation. A chronic motor or sensory neuropathy is also a possible phenotype of the disease as well as asymptomatic patients. A large deletion of 1.5 Mega basepairs on Chr17p11.2–12 was found to be the reason for HNPP. This deletion results in a lower expression of peripheral myelin protein-22 (PMP 22) which is an important protein for the myelin of Schwann cells.
Case report: We report about a six-year-old boy with progressive deafness of unknown origin. A cochlea implant was planned. Searching for the reason of the deafness we found mild peripheral neuropathy with reduced motor nerve conduction velocity. The MR of the brain showed demyelinated lesions and CSF protein was elevated. Biopsy of the suralis nerve demonstrated thickenings of the nerve, called tomaculae, which are typical for HNPP. The moleculargenetic investigation is continuing.
Conclusion: HNPP was thought to be a disease of the periphery nerve only. So far, expression of peripher Myelin-Protein-22 (PMP22) due to the deletion in chromosome 17 could be detected mainly in periphere myelin. Indeed our patient has a peripheral neuropathy and the nerve biopsy shows typical signs of HNPP (tomacula). However, the boy also has deafness and demyelination of the CNS. Only few reports of central manifestation of HNPP exist, with similar signs as in our patient. Because there were no signs of any other disease, we assume that PNP 22 has also influence of central myelination or the described chromosomal deletion is responsible for the expression of a other unknown protein with a central function.
Keywords: hereditary neuropathy, pressure palsies, demyelination in CNS, myelin protein-22