- GLI3 (associated with Greig cephalopolysyndactyly syndrome)
- SHH
- FGF
- ALX4
- 5'HoxD
- ZNF141
- MIPOL1
- IQCE
- PITX1
Prevalence:
- Represents 45% of congenital foot anomalies.
- Incidence of 1.7 per 1000 live births.
- No sex predilection.
- Postaxial – Most common, constituting 80% of duplications.
- Preaxial – 15% of duplications.
- Central – 5% of duplications.
- About 30% of patients with isolated polydactyly have a positive family history.
- Syndromes that feature polydactyly include Ellis-van Creveld syndrome, trisomy 13 syndrome, tibial hemimelia, trisomy 21 (Down syndrome), and Greig cephalopolysyndactyly syndrome.
- Patients of African descent have a higher incidence rate of 3.6-13.9 per 1000 live births.
Grade / classification system:
- Classified according to its location as preaxial (first ray), central (middle rays), or postaxial (fifth ray).
- Temtamy and McKusick classification – This classifies cases as preaxial, postaxial, or complicated and is used by geneticists.
- Venn-Watson (V-W) classification – Based on the shape of the associated metatarsal bone.
- Normal metatarsal with distal duplication
- Block metatarsal
- Y-shaped metatarsal
- T-shaped metatarsal
- Normal metatarsal shaft with a wide head
- Ray duplication
- Watanabe-Fujita classification of medial ray polydactyly.
- Tarsal
- Metatarsal
- Proximal phalangeal
- Distal phalangeal