[Hereditary neuropathy with liability to pressure palsies (tomaculous neuropathy). Clinical, electrophysical and molecular study of two affected families].

INTRODUCTION

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal-dominant disorder of peripheral myelin characterized by episodes of recurrent mononeuropathies usually involving nerves at common sites of entrapment and compression. Additional features include evidence of a diffuse demyelinating sensorimotor polyneuropathy on nerve conduction studies, focal myelin thickening (tomacula) on sural nerve biopsy, and a 1.5 Mb deletion on 17p11.2 encompassing the peripheral myelin protein 22 (PMP22) gene in most families.

PATIENTS AND METHODS

Two girls, aged 10 and 12 years, presented with peroneal nerve palsy and peroneal nerve palsy plus tibial nerve palsy, respectively. In none case, a clear causal factor was recognizable. Neurophysiological studies: both cases showed diffuse sensory and motor nerve conduction velocity slowing and prolongation of distal motor latencies. In addition, features of focal entrapment neuropathy were obtained at proximal peroneal nerve level. Sural nerve biopsy: large axons demyelination, redundant myelin and intraaxonal looping (case 1) and tomaculas (case 2). Molecular genetics: 17p12-p11 deletion was demonstrated in both affected girls, the mother and two maternal uncles of case 1 and in the father, paternal grandfather and two paternal uncles of case 2.

CONCLUSIONS

NHPP should be suspected in cases of peripheral neuropathy without clearly recognizable cause. Electrophysiological and molecular studies permit both delineation of the condition and identification of otherwise clinically normal family members.