Dear Sir, The five-fingered hand anomaly has been classified on morphological grounds as a type of triphalangeal thumb. Buck-Gramcko (1998), based on the morphology of the anatomical structures of the triphalangeal thumb, described a teratogenic sequence of the anomaly from the most rudimentary triangular middle phalanx to a fully developed five-fingered hand. However, recent advances in the understanding of developmental processes have shown that morphologically similar structures may result from different embryological processes.
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