Clinical, neurophysiological and pathological findings of HNPP patients with 17p12 deletion: a single-centre experience.

Background: Classic clinical manifestations of HNPP are characterized by recurrent painless mononeuropathies, but a minority of patients present with an atypical clinical pattern, including CMT-like neuropathy, acute or chronic inflammatory demyelinating neuropathy-like polyneuropathy, and carpal tunnel syndrome. Electrophysiological examination plays a central role in the diagnosis of HNPP, disclosing a non-uniform conduction slowing, more pronounced at entrapment sites.

Patients And Methods: We report clinical, electrophysiological and pathological findings from 73 patients with HNPP, coming from 53 unrelated families, followed at our Institute of Neurology over a 20-year period.

Results: Typical presentation with recurrent multiple mononeuropathies was observed in 28/64 (44%) patients. In the remaining 36/64 (56%), we observed an atypical clinical presentation, characterized by generalized weakness and cramps, chronic ulnar neuropathy, carpal tunnel syndrome, chronic sensory polyneuropathy, Guillain-Barrè-like presentation, and CMT-like presentation. Nine patients were asymptomatic for neuropathic symptoms. Nerve conduction studies showed in all cases a sensori-motor demyelinating polyneuropathy with conduction abnormalities preferentially localized at common entrapment sites. When performed, sural nerve biopsy disclosed the focal thickening of the myelin sheath in all patients.

Conclusions: About half of the patients with HNPP from our cohort showed an atypical clinical presentation. Neurophysiological examination represents the main tool for a proper diagnosis.