Polydactyly (Extra Fingers or Toes)

Polydactyly is the medical term for having extra fingers or toes (digits). You might also see it referred to as hyperdactyly. It’s one of the most common birth defects that affects babies’ hands and feet. Polydactyly (pronounced “paa-lee-dak-tuh-lee”) that causes extra fingers to form on your child’s hand is a form of congenital hand difference.

Using an ultrasound, your healthcare provider may be able to see that your baby has polydactyly before they’re born. But the official diagnosis will happen right after they’re born. Polydactyly can occur on its own, but it may also be part of a genetic disorder. Your baby’s provider will immediately look for signs of other conditions.

You may be a little worried if your baby is born with polydactyly. But having extra digits won’t cause them any symptoms or discomfort. Your baby’s healthcare provider can easily remove the extra finger or toe. If your baby is diagnosed with another genetic condition, they’ll need other types of treatment and care.

Types of polydactyly

There are three main types of polydactyly. The type depends on which digit has an extra version. The types are:

• Preaxial polydactyly. An extra thumb or big toe. Healthcare providers sometimes refer to an extra thumb as radial polydactyly and an extra big toe as tibial polydactyly.
• Central polydactyly. An extra finger or toe near the middle digits — between the index, middle or ring fingers or any of the toes that aren’t the big or pinkie toe.
• Postaxial polydactyly. An extra pinkie finger or pinkie toe. Providers sometimes refer to an extra pinkie finger as ulnar polydactyly and an extra pinkie toe as fibular polydactyly.

Symptoms of polydactyly

The only symptom of polydactyly is your child having more than five fingers or toes on their hand or foot. The extra digits will be visible at their birth.

Depending on which type of polydactyly your baby has, their extra fingers or toes might be fully developed and look like the rest of their digits. But the additional digits are usually less developed than typical fingers or toes, and might be attached by only skin or nerves.

Polydactyly causes

A change to your baby’s genes while they’re developing causes polydactyly. Genes are the biological building blocks that you pass down to your children. They contain instructions for the function and growth of every cell in your body.

Anything that interrupts a gene while your baby is developing can cause changes in their body. Sometimes, these changes are things we never notice, and other times, they cause issues like polydactyly and other congenital (present at birth) conditions.

If something disrupts the genes that are responsible for developing your baby’s hands and feet, there’s a chance they might be born with polydactyly. Genetic disorders can interfere with these genes, but so can environmental factors (things that happen to or around someone who’s pregnant).

Genetic disorders that may occur with polydactyly include:

• Carpenter syndrome
• Down syndrome
• Fanconi anemia

Risk factors for polydactyly

Polydactyly can affect anyone, but the condition occurs in certain babies more than others. Risk factors for developing extra fingers or toes include:

• Sex. Male babies are more likely to develop polydactyly than female babies.
• Ethnicity. Polydactyly is 10 times more common in Black male babies than white male babies. The condition is 22 times more common in Black female babies than white female babies.
• Family history. Your baby may be more likely to have polydactyly if you have a family history of genetic disorders, especially if any immediate relatives were born with extra fingers or toes.

How doctors diagnose polydactyly

Your healthcare provider may be able to diagnose polydactyly with an ultrasound test before your baby is born. Otherwise, your baby’s provider will be able to diagnose the condition when your baby is born. They’ll identify any extra digits on your child’s hands or feet and will diagnose a type of polydactyly.

Depending on the type of polydactyly, your baby might need a hand X-ray or foot X-ray before receiving treatment.

Genetic testing for polydactyly

If you have a biological family history of polydactyly, you may want to speak with a genetic counselor. They can help you decide if genetic testing is right for you. Genetic testing can screen for gene variants, including the variants that cause polydactyly.

If you’re the carrier of a genetic variant, it doesn’t necessarily mean your child will develop a genetic disorder. A genetic counselor can explain your risk and what you can do to protect your health or reduce your risk of passing genetic issues on to your children.

How is polydactyly treated?

Treatment for polydactyly depends on the type of condition your baby has, but it usually involves removing the extra digit from your child’s hand or foot. There are a few different ways to remove the extra finger or toe. These methods include:

• Surgical ligature. Your baby’s provider will tie a tight string or band around the base of the extra finger that cuts off its blood supply. A week or two later, the extra finger will fall off.
• In-office excision. Your baby’s provider will numb the skin around your child’s extra digit with an injection. Then, they’ll use a cautery device to remove the extra finger or toe.
• Polydactyly surgery. If your baby’s polydactyly is on their feet or they’re not a good candidate for surgical ligature or in-office excision, they’ll need to have their extra digit surgically removed.

When should my baby see their healthcare provider?

If you notice any changes in your baby’s digits, make a call to their provider. It’s important that your baby sees their provider if they have any pain or if the removal site has any of the following symptoms:

• Bleeding
• Leaking fluid or discharge
• Skin discoloration
• Swelling

What can I expect if my baby has polydactyly?

Don’t worry if your baby has polydactyly. You can expect them to make a full recovery after they have the extra digit removed. The removal process will have no impact on their future growth or development.

If your child has another birth defect or genetic condition, they might need other types of treatment or care. Talk to their healthcare provider about what to expect in the future.