This is the most extreme case of polydactyly I’ve seen — a child in China born with 31 fingers and toes.
They’re hoping to carry out a surgical correction, which can cause new problems…but in this case it’s necessary, because apparently the child’s thumbs have been transformed into other digits, or failed to form, so all they’ve got is 15 fingers. Opposable thumbs are generally useful.
Oh, and look at those big toes — triphalangeal digits? Developmentally fascinating, personally tragic.