Polydactyly is extra digits (fingers or toes) that are present at birth (congenital). A baby born with polydactyly will have more than 5 digits on one or both of their hands or feet. Polydactyly can occur without any other complications (isolated polydactyly) or it can be seen in a baby who has many abnormal features as part of a syndrome (syndromic polydactyly). Typically, the extra digit is a small piece of soft tissue that can be easily removed with surgery. Sometimes, the extra digit will contain bones or even be an entire functioning digit. There are three main forms of polydactyly. The most common form has the extra digit located on the side with the small digit (ulnar or postaxial polydactyly). Another form has the extra digit located on the side with the large digit - the thumb or big toe (radial or preaxial polydactyly). The third form, which is rare, causes an extra middle digit (central polydactyly)
Isolated polydactyly is an autosomal dominant genetic condition. This means that a mutation (change) in one of the two copies of a gene causes polydactyly. Mutations in many different genes can cause isolated polydactyly. There are also at least 39 different syndromes that have polydactyly as one of their features. Isolated polydactyly occurs much more often in African American people. Polydactyly can be easily diagnosed with a physical exam performed by your baby’s doctor. If your baby has other features in addition to polydactyly that may suggest a syndrome, or if you have a strong family history of isolated polydactyly (many affected family members), an evaluation by a geneticist and genetic counselor can be beneficial. Treatment of polydactyly usually involves surgical removal of the extra digit. However, the type of surgery your baby may need varies greatly and depends on both the location and type of polydactyly. If your baby has polydactyly, talk with your doctor to discuss the best treatment plan.