About Polydactyly
During the first trimester of gestation, a fetus's hand development starts as paddles which will later separate into 5 fingers. In case of an error in this process, Polydactyly happens. In most cases, a specific cause has not been identified. Sometimes genetic abnormalities or hereditary syndromes cause this. If polydactyly is not passed down, it occurs due to a change in a baby’s genes while it is in the womb.
What is Polydactyly?
Polydactyly is a condition where a person is born with more than the usual number of fingers or toes. Polydactyly, also known as hyperdactyly, is a medical condition characterized by the presence of extra fingers or toes. The term “polydactyly” comes from the Greek words “polys,” meaning “many,” and “daktylos,” meaning "digits". Polydactyly is one of the most common birth defects affecting babies’ hands and feet1. It can occur in various forms, with the extra digit being fully formed and functional, partially formed with some bone, or just a small mass of soft tissue2. The extra digit often grows next to the fifth finger or toe. There are several types of polydactylies, classified by the position of the extra digit:
Preaxial (radial/tibial) polydactyly: An extra thumb or big toe.
Central polydactyly: An extra finger or toe near the middle digits.
Postaxial (ulnar/fibular) polydactyly: An extra pinkie finger or toe.
Polydactyly can affect any newborn baby, but it’s more common in African babies and male babies. It can also be associated with certain genetic disorders. Despite being one of the most common congenital conditions, these issues as a whole are still relatively rare.
Who does polydactyly affect?
Polydactyly can affect any newborn baby. It is one of the most common congenital conditions, which means it is present from birth. However, these issues as a whole are still relatively rare. African babies are 10 times more likely than white babies to be born with polydactyly. In addition, male babies are more likely to be born with polydactyly than female babies.
Your child might be more likely to develop polydactyly if you have a family history of genetic disorders — especially if any of your immediate relatives (like your biological grandparents, parents, or siblings) were born with extra fingers or toes. Being born with extra digits doesn’t guarantee your child will have developmental disorders or any other conditions. Around 1 in 1,000 babies born each year has some form of polydactyly. Even if it’s one of the most common congenital conditions, these issues as a whole are still relatively rare.
What are the symptoms of polydactyly?
The symptoms of polydactyly can vary, and the extra digit or digits may be:
A small, raised lump of soft tissue, containing no bones (called a nubbin)
A partially formed finger or toe containing some bones but no joints
A fully functioning finger or toe with tissues, bones, and joints
There are three main types of polydactylies:
Ulnar or postaxial polydactyly or small finger duplication: This is the most common form of the condition, where the extra finger is on the outside of the little finger. This side of the hand is known as the ulnar side. When this form of the condition affects the toes, it is called fibular polydactyly.
Radial or preaxial polydactyly or thumb duplication: This is less common, occurring in 1 in every 1,000 to 10,000 live births. The extra finger is on the outside of the thumb. This side of the hand is known as the radial side. When this form of the condition affects the toes, it is called tibial polydactyly.
Central polydactyly: This is a rare type of polydactyly. The extra finger is attached to the ring, middle, or most often index finger. This form of the condition has the same name when it affects the toes.
Polydactyly may be passed down in families. When polydactyly is passed down, it is known as familial polydactyly. This form of polydactyly typically happens in isolation, meaning a person may not experience any associated symptoms.
What are the types of Polydactyly?
Ulnar or post-axial polydactyly or small finger duplication: The most common form of Polydactyly, which causes an extra finger on the outside of the little finger.
Radial or pre-axial polydactyly or thumb duplication: This less common form occurs on the outside of the thumb.
Central polydactyly: This is a rare type of polydactyly. During this, the extra finger is attached to the ring, middle, or most often index finger.