Deletion of 17p11.2 chromosome in Spanish families with hereditary neuropathy and abnormal sensitivity to pressure

Hereditary neuropathy with abnormal liability to pressure palsies (HNPP) is a dominant autosomally transmitted disease that gives rise to foci of peripheral nerve myelination, reducing conduction and leading to episodes of palsy and sensory changes that are all linked to sensitivity to pressure and traction on the affected nerve roots. The molecular basis of HNPP has been identified as a submicroscopic deletion of the 17p11.2 chromosome in exactly the same region that it is duplicated in Charcot-Marie-Tooth disease, type 1A (CMT1A). We report genetic analyses of 13 patients (belonging to 3 families) diagnosed of HNPP by means of physical examination and electrophysiologic and morphologic tests (the last in 3 cases only). Inter- and intrafamilial variation in symptomatology was studied. Some patients presented the usual clinical signs, such as recidivating brachial plexus palsy, permanent sensory polyneuropathy, foot deformities and others that might also be found in patients with CMT1A. All the patients showed electrophysiologic signs of underlying demyelinating polyneuropathy. Genetic study centered on detecting the deletion of 17p11.2 by segregation analysis with the polymorphic markers VAW409R3a (D17S122) and EW401HE (D17S61). Our results confirmed deletion at the CTM1A location of chromosome 17p11.2 in all 13 patients examined. These data suggest that the deletion of 17p11.2 plays a causal role in HNPP and that it is the most prevalent mutation in this disease; our findings constitute new evidence of the importance of the CMT1A/HNPP locus in the formation and control of peripheral myelin and in the ultimate functioning of peripheral nerves.