Bardet-Beidl syndrome is associated with polydactyly and syndactyly in the fingers and toes.Saethre-Chotzen syndrome involves a double first toe and syndactyly between the second and third fingers.Carpenter syndrome involves a pointed head with polydactyly occurring in the fifth finger or the first or second toe.Fused digits or extra digits or an abnormally wide thumb or big toe also occur. Greig syndrome involves abnormal development of the limbs, head, and face.Acrocephalosyndactyly involves early fusion of skull bones and syndactyly.A 2017 study estimated that this occurs in 1 in 2,000 to 3,000 births. Syndactyly involves digits that are fused or weblike.Down syndrome is strongly associated with double thumbs.Here are a few of the genetic syndromes associated with polydactyly: With this detailed understanding of the genetics, doctors are better able to look for and treat other conditions in children born with polydactyly. The 2010 study identified mutations in 99 genes associated with some of these conditions. A 2010 study of polydactyly classification found 290 associated conditions.Īdvances in genetic techniques have made it possible to identify specific genes and mutations that contribute to many of these disorders. There are many rare syndromes associated with polydactyly, including cognitive and developmental abnormalities and head and face malformations. A 1998 study of 5,927 people with polydactyly found that only 14.6 percent of them had been born with an associated genetic disorder. Syndromic polydactyly is much less common than isolated polydactyly. It’s the least common type.Īs genetic technologies have advanced, researchers have classified subtypes based on variations in the malformation and the genes involved. Central polydactyly occurs in the middle digits of the hand or foot. ![]() In the hand, this is called the radial side. Preaxial polydactyly occurs on the inside of the hand or foot, where the thumb or big toe is.This is the most common type of polydactyly. In the hand, this is called the ulnar side. Postaxial polydactyly occurs on the outside of the hand or foot, where the fifth digit is.There are three types of isolated polydactyly, classified by the position of the extra digit: Sometimes it is associated with another genetic condition. This is called isolated or nonsyndromic polydactyly. Polydactyly most often occurs without other abnormalities.
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