To study the clinical and electrophysiological features of the patients with hereditary neuropathy with liability to pressure palsy (HNPP) diagnosed by gene analysis.

Seven patients from two HNPP families were assessed on medical history, physical examination, electrophysiology findings and gene analysis.

A clinical manifestation of acute, painless, recurrent peripheral nerve palsies was typical for HNPP. Median, ulnar and peroneal nerves were usually affected. Electrophysiology study revealed that prolonged distal motor latency and slowing nerve conduction velocity were prominent. Gene studies exhibited a deletion of the peripheral myelination protein 22 gene in all the seven patients.

HNPP usually affects areas where nerves are subject to entrapment, and many episodes are preceded by minor compression on the affected nerve. As a reliable screening tool in detecting HNPP, the electrophysiological study shows that segmental demyelination is most commonly seen at common nerve entrapment sites.

Hereditary sensory and motor neuropathy; Myelin proteins; Gene deletion; Electrophysiology; Polymerase chain reaction