Revertant somatic mosaicism is a recognized phenomenon in patients with epidermolysis bullosa (EB) and other inherited diseases.1 It occurs when spontaneous mutations result in correction of a germline mutation that underlies the genodermatosis, leading to phenotypic reversion and sometimes functional improvement.2 Revertant mosaicism occurs though several mechanisms, all causing a nonreciprocal transfer of genetic information from the parent cell to the daughter cells. Gene conversions, intragenic crossover, back mutation, and second-site mutation (eg, single-base substitution) have all been described as mechanisms, and multiple mechanisms may occur in different cell populations in the same individual. True forward somatic mosaicism, however, has not to our knowledge been described previously in EB. Forward, or nonrevertant, mosaicism occurs during embryogenesis, when a mutation occurs in mitosis affecting only that subsequent cell line and not the other dividing cells of the embryo. The later it occurs during embryogenesis, the fewer cells will be affected.