Charcot-Marie-Tooth disease type 1A (CMT1A) accounts for 70-90% of cases of CMT1 and is most frequently caused by the tandem duplication of a 1.4-Mb genomic fragment on chromosome 17p12.
We have described a novel mutation in the first extracellular loop of PMP22 associated with an atypical CMT1A that overlaps pathologically with CMT1B caused by point mutations in the extracellular domain of P0.
While mutation in the gene encoding the major myelin protein, P0 has been associated with CMT1B, CMT1A and HNPP have been shown to be associated with reciprocal recombination events leading either to a large submicroscopic duplication in CMT1A, or the corresponding DNA deletion in HNPP.