การตรวจวิเคราะห์จ านวนชุดของยีน PMP22 ในโรคพันธุกรรมความผิดปกติของระบบประสาท ส่วนปลายที่พบบ่อย: CMT1A and HNPP Determination of PMP22 Gene Copy Number in Two Common Inherited Peripheral Neuropathies: CMT1A and HNPP

Charcot-Marie-Tooth disease type 1A (CMT1A) and hereditary neuropathy with liability to pressure palsy (HNPP) are two common inherited peripheral neuropathies caused by duplication and deletion, respectively of 1.5 Mb region on chromosome 17p11.2 encompassing peripheral myelin protein 22 (PMP22) gene. The disease phenotypes reflect the effect of the overand under-expressed PMP22 protein on the peripheral nervous system (PNS) myelin formation and maintenance. Determination of PMP22 gene copy number is important for diagnostic purpose and genetic counseling. We describe here the genetic testing for both diseases by application of initially quantitative real-time PCR and finally semi-quantitative multiplex PCR/DHPLC techniques. We studied the PMP22 gene dosage in 90 unrelated patients with suspected CMT1A or HNPP. Only 19 (15.2%) and 4 (3.2%) patients carried the PMP22 duplication and PMP22 deletion, thus being definitely diagnosed as CMT1A and HNPP, respectively. We found that both molecular techniques were sensitive, reproducible and reliable, but semi-quantitative multiplex PCR/DHPLC was simpler, faster and cheaper, thus more effective to be used in a routine laboratory. The low detection rate in our study may imply the highly genetic heterogeneity of the Charcot-Marie-Tooth disease. However, this finding stresses the necessity of an accurate molecular diagnosis for the diseases. ค าส าคญ: ยน PMP22, โรค CMT1A, โรค HNPP, จ านวนชดของยน, ดเอชพแอลซ