Crossed polysyndactyly is a very rare type of polysyndactyly, a genetic condition present at birth in which individuals are born with webbed or fused extra fingers or toes. In crossed polysyndactyly, the extra fingers may be on the pre-axial side of the hand (thumb side) while in the foot of the same individual, the extra toes/s would be on the postaxial side (little toe side). There is typically also syndactyly of the extra fingers and toes which means they are fused together with excess skin. This condition has been shown to run in families and is inherited as an autosomal dominant trait. This means that an individual only needs to have one copy of the changed gene that causes crossed polysyndactyly and is inherited from a parent that also has the trait. A person with crossed polysyndactyly has a 50% chance of passing it on to each of his or her children. Surgery may be used to remove the extra fingers or toes for cosmetic or functional reasons. Crossed polysyndactyly is not usually seen with any additional findings or abnormalities. If your baby has crossed polysyndactyly, talk with your pediatrician about available treatment options. See also Polysyndactyly.