[Molecular genetic diagnosis of Charcot-Marie-Tooth disease and hereditary neuropathy with liability to pressure palsies].

Charcot-Marie-Tooth (CMT) disease is the most commonly inherited disorder of the peripheral nervous system; in Norway, the estimated prevalence is approximately one in 2,500. CMT has been classified into a demyelinating form (CMT1) and an axonal form (CMT2). Around 70-80% of CMT1 cases are caused by a dominantly inherited 1.5 Mb duplication at 17p11.2-12 (CMT1A), encompassing the peripheral myelin protein 22 (PMP22) gene. In contrast, hereditary neuropathy with liability to pressure palsies (HNPP) is caused by the reciprocal deletion of the same 1.5 Mb region. We recently developed a method by real-time quantitative polymerase chain reaction (PCR) for detecting CMT1A duplication and HNPP deletion. Real-time quantitative PCR is very sensitive for identifying PMP22 gene copy number in CMT1A duplication and HNPP deletion. We discuss molecular genetic testing of CMT1A duplication and HNPP deletion. Real-time quantitative PCR should find broad application in clinical and research settings, not only in CMT1A duplication and HNPP deletion, but also in other diseases involving gene copy number or gene expression.