Clinical, Electrophysiological and Molecular Features in Hereditary Neuropathy with Liability to Pressure Palsies

Abstract

Introduction: Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal-dominant inherited peripheral neuropathy caused by deletions of the PMP22 gene (PMP22). It is classically characterized by episodes of repeated focal pressure neuropathies at common entrapment sites. Atypical forms are recognized and may occur in up to 56% of HNPP patients. The electrophysiological characteristics and the genetic studies are paramount for its diagnosis. We aim to describe clinical, electrophysiological and genetic features of a cohort of patients diagnosed with HNPP at a tertiary hospital. Methods: Retrospective study of patients with a confirmed diagnosis of HNPP, using descriptive statistics for their characterization. Results: Seventeen patients from 15 different families were included. Nine were males, and the overall mean age was 42.6 years-old. Age at first symptoms ranged from 3 to 46 years-old, with mean time until diagnosis of 9.3 years. Nine patients (53%) presented recurrent painless mononeuropathies or isolated focal compressive neuropathies, and eight patients (47%) had atypical presentation phenotypes, such as “Charcot-Marie-Tooth-like (CMT-like) and sensory neuropathy. Intra-familial clinical heterogeneity was observed. All patients showed nerve conduction slowing at common entrapment sites (median, ulnar and peroneal nerves), and signs of a more generalized peripheral nerve involvement were present in more than half of the patients. Fifteen patients carried the PMP22 gene deletion, and point mutations were present in two. Conclusion: Our cohort presents similar clinical characteristics to the literature description, with a significant proportion of patients with atypical presentations. The absence of clinical-electrophysiological correlation emphasise the importance of nerve conduction and genetic studies for the definite diagnosis of the disease.