Polydactyly (pol-ee-DAK-tuh-lee) is when a baby is born with an extra finger on the hand or an extra toe on the foot. It can be on one or both hands or feet.
Polydactyly usually happens on the pinky finger side of the hand or little toe side of the foot (called "post-axial"). Less often, it happens on the thumb or big toe side ("pre-axial"). Rarely, it can be central or in the middle of the hand or foot. The extra digit is usually smaller than the other fingers or toes.
Polydactyly happens before a baby is born. When a baby's hands and feet are first forming, they're shaped like mittens. Then the fingers or toes form. If an extra finger or toe forms, this causes polydactyly.
Any baby can be born with polydactyly. Post-axial polydactyly can run in families.
Most babies who have polydactyly do not have other health problems. But sometimes, it happens as part of a genetic syndrome .
Polydactyly may be seen before birth on an ultrasound. Otherwise, doctors diagnose it when the baby is born.
Sometimes doctors do X-rays to see if the extra digit has bones and joints. This helps the surgeon decide what kind of treatment is needed.
Treatment for polydactyly depends on the location of the digit on the hand or foot and how it is formed. An extra pinky or little toe that is connected with a thin stalk can be removed easily, sometimes right in the surgeon's office with a surgical clip or stitch.
Extra thumbs, big toes, or middle fingers or toes that contain bones and/or joints need surgery in the hospital.
Because surgery for polydactyly is usually done when a baby is young, most kids learn to use their hands and walk without problems. If needed, occupational therapy (OT), physical therapy (PT), and home exercises can help a child with this.
Reviewed by: Jennifer M. Ty, MD
Date Reviewed: Jun 1, 2018
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