How rare is polydactyly?

Polydactyly, which is the presence of extra fingers or toes, is a relatively rare condition. In the opening paragraphs, we’ll provide some quick answers to key questions about the prevalence of polydactyly to help readers get an overview of this topic.

What percentage of people have polydactyly?

Polydactyly affects around 1 in every 500 to 1,000 births. So the prevalence is estimated to be around 0.1% to 0.2% of live births. This makes it a fairly uncommon condition.

What are the chances of being born with polydactyly?

Since polydactyly affects about 1 in every 500 to 1,000 births, the chances of a baby being born with extra fingers or toes is around 0.1% to 0.2%. That means for every 1,000 babies born, 1 or 2 babies on average will have polydactyly.

Is polydactyly hereditary?

Polydactyly often runs in families and can be passed down genetically. Having a family member with polydactyly increases the chances that a baby will also be born with extra digits. However, polydactyly does not always have a clear hereditary link.


In summary, polydactyly is considered a rare condition, affecting around 0.1% to 0.2% of the population. The chances of a baby being born with extra fingers or toes is fairly low, around 1 in 500 to 1,000 births. While polydactyly can be hereditary in some cases, it does not always run in families.

Prevalence of polydactyly by type

There are different types of polydactyly that can occur:

Postaxial polydactyly

This is the most common type of polydactyly, accounting for about 80% of cases. It occurs as an extra little finger on the pinky side of the hand or an extra little toe on the outside of the foot. Around 1 in 3,000 Caucasian live births have postaxial polydactyly.

Preaxial polydactyly

This type accounts for about 10% of polydactyly cases. It involves an extra thumb on the thumb side of the hand or an extra big toe on the inside of the foot. It’s rarer than postaxial, affecting around 1 in 10,000 Caucasian live births.

Central polydactyly

This is the rarest type, making up around 5% of cases. It occurs when an extra finger arises between the normally present digits, rather than on the preaxial or postaxial side. Approximately 1 in 50,000 Caucasian live births have central polydactyly.

Syndromic polydactyly

Around 15% of polydactyly cases are associated with genetic syndromes like Down syndrome, Ellis-van Creveld syndrome, and Bardet-Biedl syndrome. These syndromes have polydactyly as one of several characteristic features.

The table below summarizes the prevalence of different polydactyly types:

Type Prevalence
Postaxial 1 in 3,000 Caucasian live births
Preaxial 1 in 10,000 Caucasian live births
Central 1 in 50,000 Caucasian live births
Syndromic Associated with genetic syndromes like Down syndrome

This illustrates that postaxial polydactyly is the most prevalent type, while central polydactyly is exceptionally rare in the general population.

Racial and ethnic differences in polydactyly prevalence

The prevalence of polydactyly varies between different racial and ethnic groups. Some key differences include:

  • African Americans have a higher prevalence of polydactyly compared to Caucasians. Around 3.6 per 1,000 African American births have polydactyly versus 1.3 per 1,000 Caucasian births.
  • Native Americans also have an elevated prevalence. Polydactyly occurs in around 3 to 4 per 1,000 Native American births.
  • Asian populations have a lower prevalence than Caucasians. Polydactyly affects around 0.5 per 1,000 Asian births.
  • The condition appears to be most common among African Americans and Native Americans, while least common in persons of Asian descent.

The reasons for these racial and ethnic differences are not fully understood. Genetic factors likely play a role. Environmental factors may also be involved.

Gender differences in polydactyly

Polydactyly occurs more frequently in males than females. The male to female ratio is around 3:2. Several large studies of polydactyly cases have reported this consistent gender difference:

  • A British study found a male to female ratio of 1.5 to 1 among polydactyly cases.
  • A study in India reported a male to female ratio of 1.9 to 1.
  • Another study in India found the male to female ratio was 1.6 to 1.

The reasons for the higher incidence in males are not well established. Sex hormones may play a role, as they are involved in limb development during gestation. The SRY gene on the Y chromosome may also contribute to the gender difference.

Global prevalence

Looking at global figures, it’s estimated that polydactyly affects around 5 million people worldwide. This figure is based on a total worldwide prevalence of around 0.2% and a current global population size of about 7.9 billion.

However, the condition appears to be more common in some parts of the world, such as India and Africa, than others. Many cases may also go undocumented, particularly in less developed regions. So the worldwide prevalence may be higher than current estimates.

Changes over time

The prevalence of polydactyly does not seem to be increasing or decreasing substantially over time based on surveillance data. The rates have remained fairly steady for the past few decades.

For instance, data from the National Birth Defects Prevention Network in the US found that the rate of polydactyly was 1.62 per 10,000 live births from 2004 to 2006. This was similar to the rate of 1.56 per 10,000 live births from 1999 to 2001.

Advances in medical care mean that more children with polydactyly now undergo reconstructive surgery to remove the extra digits shortly after birth. So while the prevalence has been stable, management has improved over time.

Associated genetic mutations and syndromes

In some cases, polydactyly arises from specific genetic mutations passed down in families. Mutations in genes such as GLI3, ZRS/SHH, MIPOL1, and GLI1 can cause inherited polydactyly.

Polydactyly also occurs as one feature of many genetic syndromes, such as:

  • Down syndrome – Caused by trisomy of chromosome 21. Polydactyly occurs in around 7% of Down syndrome cases.
  • Ellis-van Creveld syndrome – Caused by mutations in EVC and EVC2 genes. Polydactyly occurs in around 60% of cases.
  • Bardet-Biedl syndrome – Linked to mutations in at least 21 genes. Polydactyly occurs in around 55% of cases.

When polydactyly occurs as part of a genetic syndrome, it is considered a secondary symptom rather than an isolated defect. The syndrome provides the underlying cause.

Polydactyly in other species

Polydactyly is reasonably common in cats, occurring in around 1 in 500 kittens. The extra toes on feline polydactyls are often referred to as “mitten paws” or “thumbcat” paws. The trait originated from a mutation that became common in certain cats brought over on ships by early New England settlers.

Polydactyly also occasionally occurs in dogs, pigs, cows, sheep, and horses. The condition appears to be rarer in most other mammal species compared to humans and cats.

There are a few isolated populations of polydactylous animals that have been widely studied:

  • A colony of polydactylous cats was established in Nova Scotia in the 1970s and their lineage has been maintained.
  • A flock of polydactylous chickens was identified in Massachusetts in the 1990s. These were bred specifically to study the genetic basis of limb deformities.

These unique animal groups provide opportunities for more research into the genetics behind polydactyly and limb development abnormalities.


The main treatment for polydactyly is surgery to remove the extra digit(s). This is normally done when the child is around 1 year old.

The surgery has good outcomes, with low recurrence rates in most cases. After surgery, function of the hand or foot generally becomes normal over time. Occasionally occupational therapy is needed to aid dexterity of the hand after extra finger removal.

If the digit is severely underdeveloped and nonfunctional, surgery may be done shortly after birth. But if the extra finger or toe is well-formed and mobile, it is often left until the child is older.

Rarely, the bones of the extra digit may be connected to bones of the normal fingers. In these cases, more complex reconstructive surgery is required.


The prognosis for isolated polydactyly is generally very good after surgery to remove the extra digits. Hand and foot function are typically normal with a low complication rate.

If polydactyly occurs as part of a syndrome, the prognosis depends on the particular syndrome. Outcomes are generally good for Down syndrome. But other rarer syndromes can have more complex health and developmental issues.

Impact on quality of life

Polydactyly can initially cause some functional impairment of the hands or feet in infants. But after surgery, normal hand and foot function is restored in the majority of cases.

The abnormal appearance can have psychosocial effects. However, the surgery typically leaves minimal scarring, and the hands or feet look normal afterwards.

Support groups such as the Polydactyly Support Group can help children and families connect with others experiencing the same condition. This provides a sense of community and reassurance.

Overall, with surgery in early childhood, most people with polydactyly go on to have very good quality of life with minimal long-term impacts.

Key takeaways

In summary, some key points about the prevalence of polydactyly include:

  • Polydactyly affects around 1 in 500 to 1,000 live births globally
  • The most common type is postaxial polydactyly
  • prevalence varies between ethnic groups, with higher rates among African Americans
  • Males are around 1.5 times more likely to have polydactyly than females
  • Cases have remained steady over time rather than increasing or decreasing
  • Polydactyly is more common but not rare, occurring in 0.1% to 0.2% of the population

While not common, polydactyly is one of the more prevalent congenital limb abnormalities. Understanding its epidemiology is important for health professionals caring for affected children and families.

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