Any evidence of rheumatoid arthritis in a patient with bilateral polydactyly
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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.
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
- 1. Delgadillo D, Adams NS, Girotto JA. Supernumerary Digits of the Hand. (2016) Eplasty. 16: ic3. Pubmed