Rare Hematology News

Disease Profile


Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.


US Estimated

Europe Estimated

Age of onset





Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease.


Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype.


dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.


recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder.


Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.


Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.


Not applicable


Other names (AKA)

Non-syndromic syndactyly


Syndactyly is a term used to describe webbed or conjoined digits (fingers or toes). It may occur as an isolated finding or may be a symptom of a genetic syndrome. There are over 300 genetic syndromes that involve syndactyly, such as Apert syndrome and Saethre-Chotzen syndrome. There are many different ways to classify or group non-syndromic (isolated) syndactyly. Presently, researchers classify the different types of syndactyly based on how severe the syndactyly is, which digits are involved, how the trait appears to run through families, and whether an underlying gene mutation has been identified. Using this system, nine different non-syndromic types of syndactyly have been defined.[1][2] 

Syndactyly is caused by a mixture of genetic and environmental factors. In about 10-40% of individuals with syndactyly, there is a family history.[3] Syndactyly can run through families in many different ways, depending on the underlying cause. When isolated, it can be inherited in an autosomal dominant, autosomal recessive, or X-linked recessive manner.[1] Treatment usually involves surgery to separate the digits.[3]


During normal embryonic (fetal) development, the hand initially forms in the shape of a paddle, and then eventually splits into separate fingers. Syndactyly results when one or more fingers fail to separate during this time.[1][4]

Research continues into further understanding why this happens. Many cases seem to occur without an apparent cause, while some may occur due to a genetic (inherited) defect, environmental exposure during pregnancy, or a combination or both factors. Syndactyly may also occur as a part of an underlying genetic syndrome and can be found in over 300 different genetic syndromes.[1][3][4]

Learn more

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The Children's Hospital of Philadelphia offers information on Syndactyly.
  • MedlinePlus was designed by the National Library of Medicine to help you research your health questions, and it provides more information about this topic.

In-Depth Information

  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.


  1. Malik, Sajid. Syndactyly: phenotypes, genetics and current classification. Eur J Hum Genet.. August 2012; 20(8):817-824. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3400728/.
  2. Jordan, D. et al. The Epidemiology, Genetics and Future Management of Syndactyly. The Open Orthopaedics Journal. 2012; 6(Suppl 1: M2):14-27. https://benthamopen.com/FULLTEXT/TOORTHJ-6-14.
  3. Deune, EG. Syndactyly. Medscape. November 3, 2015; https://emedicine.medscape.com/article/1244420.
  4. Syndactyly. Children's Hospital Boston. 2009; https://www.childrenshospital.org/az/Site1036/mainpageS1036P0.html. Accessed 12/15/2016.

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