Hereditary Neuropathy With Liability to Pressure Palsies and Inherited Brachial Plexus Neuropathy-Two Genetically Distinct Disorders

To determine whether hereditary neuropathy with liability to pressure palsies (HNPP) and inherited brachial plexus neuropathy (IBPN) are genetically distinct disorders and to evaluate the usefulness of fluorescence in situ hybridization (FISH) for diagnosing HNPP in individual patients. We studied representative metaphases from patients with HNPP and IBPN with use of FISH and a DNA probe. With use of FISH, 14 persons from 4 unrelated families with HNPP and 7 members from 3 unrelated families with IBPN were studied. We used a DNA probe that hybridizes to chromosome 17p 11.2 in an area thought to be deleted in HNPP. Each participant in this study who had HNPP showed deletion of this chromosome site. Each of the 10 control subjects and 7 patients with IBPN showed normal fluorescent signals on both number 17 chromosomes. These results demonstrate that HNPP and IBPN are genetically different. FISH with this probe is a sensitive and specific method for detect­ing the chromosomal deletion in individual patients without the use of family studies or linkage analysis.