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Hereditary neuropathy with liability to pressure palsies(HNPP)is commonly associated with a 1.5-megabase deletion on chromosome 17p11.2-12.We analyzed the phenotypic expression of the deletion in 39 HNPP patients from 16 families carrying the deletion.Two-thirds of the individuals had episodes of acute mononeuropathy,often involving nerve territories of the upper limbs or brachial plexus;however,41%of affected subjects were unaware of their disease,and 25%were almost or totally free of symptoms; one-third complained of chronic symptoms and four older patients had a picture of polyneuropathy.Electrophysiologic abnormalities differed among affected subjects,ranging from conduction abnormalities localized at common entrapment sites to diffuse conduction slowing,usually more evident at entrapment sites;patients from one family had preeminent proximal involvement.The spectrum of phenotypic expression of deletion-associated HNPP appears to be broader than previously thought.The prevalence of the disease is probably underestimated,and the availability of molecular diagnosis should increase disease detection. |
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