Mirror polydactyly: pathogenesis based on a morphogen gradient theory.

We report on an infant with 7 toes of the left foot in a mirror configuration in association with ipsilateral duplication of the calcaneus and fibula, tibial aplasia, femoral hypoplasia, and a teratomatous sacrococcygeal tumour. The possible pathogenetic mechanisms leading to this limb abnormality are discussed with special emphasis on a field morphogen gradient hypothesis.