Post-axial polydactyly

Last revised by Dr Dai Roberts on 24 Apr 2021

Post-axial polydactyly refers to polydactyly where the additional digit is on the ulnar margin of the hand, or lateral to the 5th (little) toe.


Post-axial polydactyly is more common than preaxial polydactyly, with an estimated incidence of 1 in 3000 5.


Post-axial polydactyly can be associated with:


The majority of cases are idiopathic. Associations with mutations to the GLI3 gene on chromosome 7 as well as a second locus mapped to chromosome 13 have been implicated in post-axial polydactyly 5.


Post-axial polydactyly has been defined by Temtamy and McKusick as:

  • type A: additional digit at the MCP joint (or more proximally at the CMC joint)
  • type B: small nubbin of non-functioning tissue or additional soft tissue on a pedicle

Or, you can use a separate three-part classification system:

  • type I: nubbin or floating digit
  • type II: duplications at the MCPJ
  • type III: duplication of the entire ray

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Cases and figures

  • Case 1
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  • Case 2
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  • Case 3: bilateral polydactyly
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  • Case 4
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  • Case 5
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