PHENOTYPIC HETEROGENEITY IN HEREDITARY NEUROPATHY WITH LIABILITY TO PRESSURE PALSIES ASSOCIATED WITH CHROMOSOME 17P11.2-12 DELETION

Hereditary neuropathy with liability to pressure palsies (HNPP) is com monly associated with a 1.5-megabase deletion on chromosome 17p11.2-12 . We analyzed the phenotypic expression of the deletion in 39 HNPP pat ients from 16 families carrying the deletion. Two-thirds of the indivi duals had episodes of acute mononeuropathy, often involving nerve terr itories of the upper limbs or brachial plexus; however, 41% of affecte d subjects were unaware of their disease, and 25% were almost or total ly free of symptoms; one-third complained of chronic symptoms and four older patients had a picture of polyneuropathy. Electrophysiologic ab normalities differed among affected subjects, ranging from conduction abnormalities localized at common entrapment sites to diffuse conducti on slowing, usually more evident at entrapment sites; patients from on e family had preeminent proximal involvement. The spectrum of phenotyp ic expression of deletion-associated HNPP appears to be broader than p reviously thought. The prevalence of the disease is probably underesti mated, and the availability of molecular diagnosis should increase dis ease detection.