Clubbed Thumb

Brachydactyly type D
Top view of a child with asymmetric brachydactyly type D thumb.
Classification and external resources
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"Clubbed thumb", also referred to as stub(by) thumb, potter's thumb or royal thumb, and known clinically as brachydactyly type D or BDD, is a harmless genetic trait characterized by the last bone of one or both thumbs being short and round with an accompanying short and wide nail bed.

It should not be confused with digital clubbing, which is a "clinical sign associated with a number of diseases."

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Wikipedia