Phenotypic variation of a new P0 mutation in genetically identical twins

We have identified a new point mutation in the myelin protein zero (P0) gen e in two genetically identical twins with a demyelinating neuropathy. The G to A transition at nucleotide position 382 caused an aspartic acid to aspa ragine substitution in exon 3. Moreover, we found clear clinical difference s which were most evident at an early age. These observations suggest that the expression of this P0 mutation may be susceptible to external, non-gene tic influences that may act early in the course of the disease to alter the phenotype.