We describe a 6-year-old girl with a T118M PMP22 mutation and heterozygous deletion of PMP22 on chromosome 17 (17p11.2-p12) resulting in a severe sensorimotor polyneuropathy.
Case Report Results: Foot pain, cavovarus feet, tibialis anterior atrophy, absent reflexes, and inability to walk were found at age 6. Nerve conduction studies showed evidence of a sensorimotor polyneuropathy and compressive mononeuropathies of bilateral median nerves at the wrist and ulnar nerves at the elbow. Genetic testing revealed a deletion of a PMP22 allele and T118M PMP22 mutation in the remaining allele.
The severe presentation of sensory motor polyneuropathy and HNPP in this patient is likely a consequence of both decreased expression of PMP22 causing features consistent with HNPP, and unopposed expression of the T118M mutant form of PMP22 that is relatively benign in the heterozygous state. The T118M mutant form of PMP22 can be disease-modifying in the appropriate circumstances. This article is protected by copyright. All rights reserved.