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

Objective: To study the clinical and electrophysiologic features of a large series of carriers of the 17p11.2 deletion. Background: The 17p11.2 deleti on is associated in most patients with recurrent acute nerve palsies, which is the typical presentation of hereditary neuropathy with liability to pre ssure palsies (HNPP). Nevertheless, a few other phenotypes have been report ed. Methods: On the basis of clinical and electrophysiologic data, the auth ors conducted a retrospective study of 99 individuals with the 17p11.2 dele tion referred to their neurogenetic department between 1993 and 1997. Resul ts: In addition to the typical presentation of HNPP, they describe five oth er phenotypes in 15 patients: recurrent positional short-term sensory sympt oms, progressive mononeuropathy, Charcot-Marie-Tooth disease-like polyneuro pathy, chronic sensory polyneuropathy, and chronic inflammatory demyelinati ng polyneuropathy-like, recurrent subacute polyneuropathy; and 14 asymptoma tic patients. In all the deletion carriers, regardless of their phenotype a nd by the second decade, the authors found a characteristic, multifocal ele ctrophysiologic neuropathy consisting of a diffuse increase in distal motor latencies contrasting with normal or moderately reduced motor nerve conduc tion velocities; a diffuse reduction in sensory nerve action potential, and multiple focal slowing of nerve conduction at the usual sites of entrapmen t. 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. Conclusion: The authors confir m the clinical phenotypic heterogeneity of the 17p11.2 deletion and suggest that electrophysiologic examination is a reliable tool for screening suspe cted HNPP patients in its various clinical presentations.