Spectrum of clinical and electrophysiologic features in HNPP patients with the 17p11.2 deletion

To study the clinical and electrophysiologic features of a large series of carriers of the 17p11.2 deletion.

The 17p11.2 deletion is associated in most patients with recurrent acute nerve palsies, which is the typical presentation of hereditary neuropathy with liability to pressure palsies (HNPP). Nevertheless, a few other phenotypes have been reported.

On the basis of clinical and electrophysiologic data, the authors conducted a retrospective study of 99 individuals with the 17p11.2 deletion referred to their neurogenetic department between 1993 and 1997.

In addition to the typical presentation of HNPP, they describe five other phenotypes in 15 patients: recurrent positional short-term sensory symptoms, progressive mononeuropathy, Charcot-Marie-Tooth disease-like polyneuropathy, chronic sensory polyneuropathy, and chronic inflammatory demyelinating polyneuropathy-like, recurrent subacute polyneuropathy; and 14 asymptomatic patients. In all the deletion carriers, regardless of their phenotype and by the second decade, the authors found a characteristic, multifocal electrophysiologic neuropathy consisting of a diffuse increase in distal motor latencies contrasting with normal or moderately reduced motor nerve conduction velocities, a diffuse reduction in sensory nerve action potential, and multiple focal slowing of nerve conduction at the usual sites of entrapment. The key diagnostic criterion is a bilateral slowing of sensory and motor nerve conduction at the carpal tunnel with at least one abnormal parameter for motor conduction in one peroneal nerve.

The authors confirm the clinical phenotypic heterogeneity of the 17p11.2 deletion and suggest that electrophysiologic examination is a reliable tool for screening suspected HNPP patients in its various clinical presentations.