Bilateral polydactyly

Case contributed by Dr Daniel J Bell


Any evidence of rheumatoid arthritis in a patient with bilateral polydactyly

Patient Data

Age: 70 years
Gender: Male

Bilateral bifid fifth metacarpals with duplication of the little fingers representing a form of post-axial polydactylism. Under the Duran classification system it would be termed a type IV-B, in view of the bifidity of the metacarpal of the little finger.

No evidence of an erosive arthropathy.

Case Discussion

Polydactyly of the hand is the presence of a supernumerary digit. It is commonly subdivided into three main types, dependent on the location of the extra digit in the hand, from commonest to rarest: post-axial (ulnar/little finger), pre-axial (radial/thumb) and central polydactyly. 

This is a case of post-axial polydactylism in view of the additional little finger, i.e. it is on the ulnar side.

Several different classification systems exist for post-axial polydactyly of the hands, including the (a) Pritsch, (b) Rayan and Al-Qattan, and (c) Duran classification systems.

Duran et al introduced their new classification system for post-axial polydactyly in 2015 1. This new classification was created as it was felt that the current systems in use were not comprehensive for coverage of the different post-axial forms.

  • type I: skin nub without nail or bone elements
  • type II: hypoplastic proximal phalanx
  • type III: proximal phalangeal malformations:
    • IIIA: bifid proximal phalanx
    • IIIB: duplicated proximal phalanx
  • type IV: metacarpal malformations:
    • IV-A: fusion of the metacarpal
    • IV-B: bifid metacarpal
    • IV-C: duplication of the metacarpal
  • type V (complicated type) with triplication of the small finger, polysyndactyly, or both
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Case information

rID: 62976
Published: 9th Sep 2018
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included
Institution: North Middlesex University Hospital

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