Philip's father, paternal aunt and uncle, and paternal grandmother were all born with polydactyly, an autosomal dominant condition where extra fingers or toes are present. Philip was born with the normal number of fingers and toes, so he was confident he had not inherited the mutation for polydactyly. Philip's wife Sarah had no family history of polydactyly, so they were surprised when their daughter Emily was born with two extra fingers and toes. The polydactyly mutation is most likely