Most common varieties are postaxial (ulnar, fibular side) and preaxial (radial, tibial side)
Postaxial (a.k.a. posterior) polydactyly
Type A: Extra digit well formed, articulates with 5th or extra metacarpal
Type B: Pedunculated postminimi, extra digit not well formed, skin tag
Synpolydactyly: Postaxial polydactyly with syndactyly often involving digits 3-4 (hands), 4-5 (toes)
Preaxial (a.k.a. anterior) polydactyly
Type I: Thumb polydactyly
Type II: Polydactyly of triphalangeal thumb
Type III: Polydactyly of index finger
Type IV: Polysyndactyly (preaxial polydactyly with syndactyly)
Crossed polydactyly: Coexistence of preaxial and postaxial polydactyly with discrepancy between axes of polydactyly between hands and feet
Rare polydactylys: Higher order polydactylys
IMAGING
General Features
Ultrasonographic Findings
Imaging Recommendations
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Gross Pathologic & Surgical Features
CLINICAL ISSUES
Demographics
Natural History & Prognosis
Treatment
DIAGNOSTIC CHECKLIST
Consider
Selected References
Kelly DM et al: Polydactyly of the foot: a review. J Am Acad Orthop Surg. 29(9):361-9, 2021
Comer GC et al: Polydactyly of the hand. J Am Acad Orthop Surg. 26(3):75-82, 2018
Holmes LB et al: Polydactyly, postaxial, type B. Birth Defects Res. 110(2):134-41, 2018
Lange A et al: A threshold model for polydactyly. Prog Biophys Mol Biol. 137:1-11, 2018
Umair M et al: Clinical genetics of polydactyly: an updated review. Front Genet. 9:447, 2018
Costa Gde A et al: Investigation of possible teratogenic effects in the offspring of mice exposed to methylphenidate during pregnancy. Reprod Biomed Online. 32(2):170-7, 2016
Khan AO et al: C8orf37 is mutated in Bardet-Biedl syndrome and constitutes a locus allelic to non-syndromic retinal dystrophies. Ophthalmic Genet. 1-4, 2016
Little KJ et al: Congenital anomalies of the hand-principles of management. Orthop Clin North Am. 47(1):153-68, 2016
Galli A et al: Distinct roles of Hand2 in initiating polarity and posterior Shh expression during the onset of mouse limb bud development. PLoS Genet. 6(4):e1000901, 2010
Slee J et al: Further evidence for preaxial hallucal polydactyly as a marker of diabetic embryopathy. J Med Genet. 34(3):261-3, 1997
Related Anatomy
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References
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Tables
KEY FACTS
Terminology
Imaging
Top Differential Diagnoses
Pathology
TERMINOLOGY
Definitions
1 or more extra digits or parts of digits
Most common varieties are postaxial (ulnar, fibular side) and preaxial (radial, tibial side)
Postaxial (a.k.a. posterior) polydactyly
Type A: Extra digit well formed, articulates with 5th or extra metacarpal
Type B: Pedunculated postminimi, extra digit not well formed, skin tag
Synpolydactyly: Postaxial polydactyly with syndactyly often involving digits 3-4 (hands), 4-5 (toes)
Preaxial (a.k.a. anterior) polydactyly
Type I: Thumb polydactyly
Type II: Polydactyly of triphalangeal thumb
Type III: Polydactyly of index finger
Type IV: Polysyndactyly (preaxial polydactyly with syndactyly)
Crossed polydactyly: Coexistence of preaxial and postaxial polydactyly with discrepancy between axes of polydactyly between hands and feet
Rare polydactylys: Higher order polydactylys
IMAGING
General Features
Ultrasonographic Findings
Imaging Recommendations
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Gross Pathologic & Surgical Features
CLINICAL ISSUES
Demographics
Natural History & Prognosis
Treatment
DIAGNOSTIC CHECKLIST
Consider
Selected References
Kelly DM et al: Polydactyly of the foot: a review. J Am Acad Orthop Surg. 29(9):361-9, 2021
Comer GC et al: Polydactyly of the hand. J Am Acad Orthop Surg. 26(3):75-82, 2018
Holmes LB et al: Polydactyly, postaxial, type B. Birth Defects Res. 110(2):134-41, 2018
Lange A et al: A threshold model for polydactyly. Prog Biophys Mol Biol. 137:1-11, 2018
Umair M et al: Clinical genetics of polydactyly: an updated review. Front Genet. 9:447, 2018
Costa Gde A et al: Investigation of possible teratogenic effects in the offspring of mice exposed to methylphenidate during pregnancy. Reprod Biomed Online. 32(2):170-7, 2016
Khan AO et al: C8orf37 is mutated in Bardet-Biedl syndrome and constitutes a locus allelic to non-syndromic retinal dystrophies. Ophthalmic Genet. 1-4, 2016
Little KJ et al: Congenital anomalies of the hand-principles of management. Orthop Clin North Am. 47(1):153-68, 2016
Galli A et al: Distinct roles of Hand2 in initiating polarity and posterior Shh expression during the onset of mouse limb bud development. PLoS Genet. 6(4):e1000901, 2010
Slee J et al: Further evidence for preaxial hallucal polydactyly as a marker of diabetic embryopathy. J Med Genet. 34(3):261-3, 1997
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