Hereditary Neuropathy with Liability to Pressure Palsies: A Report of Two Cases

Abstract

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal-dominant disorder characterized by self-limited, recurrent compressive mononeuropathies at common entrapment sites precipitated by trivial injuries. This disorder typically develops in early adulthood. Electrodiagnostic studies revealed diffuse mild demyelinating neuropathies with entrapment over common entrapment sites. Nerve biopsies frequently show segmental demyelination and thickening of the myelin sheath which is mostly caused by 1.5 Mb deletion of the 17p 11.2 site containing the peripheral myelin protein 22 (PMP22) gene on the 17(superscript th) chromosome. This report describes the clinical features, electrodiagnostic studies, and genetic studies of a Taiwanese family. Among the 5 members evaluated, 1 latent and 2 symptomatic cases had generally decreased nerve conduction velocities with further focally decreased conduction velocities or conduction blocks at common entrapment sites. Genetic studies demonstrated deletion of the Charcot-Marie-Tooth type IA sequences in 17p 11.2 in all 3 patients. Our case studies suggested that diagnosis of HNPP can be based on clinical suspicion, positive family history, and electrodiagnostic tests; however final confirmation should be based on genetic study.