ASIAN HEREDITARY NEUROPATHY PATIENTS WITH PERIPHERAL MYELIN PROTEIN-22 GENE ANEUPLOIDY

Japanese hereditary neuropathy with liability to pressure palsy (HNPP) patients have a deletion of one peripheral myelin protein-22 (PMP22) gene region in distal chromosome band 17p11.2 as do Caucasian patients , Japanese and Asiatic Indian CMT1A patients have a PMP22 gene duplica tion that results in Charcot-Marie-Tooth disease type LA (CMT1A; HMSNI A) in patients of European and Middle Eastern ancestry, About 70% of J apanese CMT1 patients have a PMP22-duplication as do Caucasians, while Japanese CMT1B, CMT2 and Dejerine-Sottas patients do not have PMP22 g ene region aneuploidy, Although HNPP and CMT1A genotypes are generated simultaneously by unequal recombination that results in PMP22 gene an euploidy in each daughter cell, only 3 Japanese HNPP probands with PMP 22 deletion from a large patient population were referred to a single center compared to 18 referred CMT1A probands with PMP22 duplication, This lower HNPP frequency more likely reflects lower HNPP reproductive fitness than patient ascertainment bias because disease severity and variation in severity is about the same in CMT1A and HNPP patients and because all patients of both types were referred regardless of diseas e severity. These results, along with an apparently high de novo CMT1A mutation rate, suggest that common ancestors of Japanese, Asian India ns, and Caucasians carried PMP22 gene-flanking sequences that enhance unequal crossing over. (C) 1995 Wiley-Liss, Inc.