AUTHOR AND EDITOR INFORMATION

Section 1 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

INTRODUCTION

Section 2 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Background

Polydactyly is the most common congenital digital anomaly of the hand and foot. It may appear in isolation or in association with other birth defects. Isolated polydactyly is often autosomal dominant or occasionally random, while syndromic polydactyly is commonly autosomal recessive.¹

Pathophysiology

Polydactyly should not be considered as a single mendelian trait but rather multifactorial. Early theories for polydactyly concerned disorders in the programmed cell death cycle of fetal limb development. Current theories focus on mutations in specific genetic locations that cause limb development to go awry. Mammals have been shown to have genetic clusters identified as homeobox or Hox genes corresponding to 5 domains across the limb bud. According to Muragaki et al,² mutations in the HOXD13 gene are associated with synpolydactyly. As limb growth in utero progresses along a preset time line, elongation of the limb, development of soft tissue, and differentiation of digits progresses.

The Medscape Genomic Medicine Research Center may be of interest.

Frequency

United States

The epidemiologic data on postaxial polydactyly is limited because most birth defect registries do not include them, preferring to focus on defects linked to teratogens. Despite being a common malformation, the true incidence of polydactyly is not fully known.

One study by Finley et al³ combined data from Jefferson County, Alabama and Uppsala County, Sweden. This study showed incidence of all types of polydactyly to be 2.3 per 1000 in white males, 0.6 per 1000 in white females, 13.5 per 1000 in black males, and 11.1 per 1000 in black females. The Swedish data alone showed polydactyly of all types to have an incidence of 1.0 per 1000, equally distributed between males and females.

While the incidence of preaxial and postaxial polydactylies has been investigated, central polydactyly has not been fully studied.

International

Genetic and ethnic factors greatly influence the nature of polydactyly in the world population. Unfortunately, the knowledge of polydactyly is limited to select studies of certain subpopulations. Preaxial polydactyly is very common in various Asian populations, accounting for 90% of cases in South China, Hong Kong, and Japan. Duplicated thumbs at the metacarpophalangeal level are the usual anomaly.^{4, 5}

Race

Postaxial hand polydactyly is a common isolated disorder in African black and African American children, and autosomal dominant transmission is suspected. Postaxial polydactyly is approximately 10 times more frequent in blacks than in whites and is more frequent in male children. In contrast, postaxial polydactyly seen in white children is usually syndromic and associated with an autosomal recessive transmission.

Other factors associated with postaxial hand polydactyly include male sex, twinning, low maternal education, parental consanguinity, and recurrence in first-degree relatives. Postaxial polydactyly is associated with Amerindian, parental subfertility, and bleeding in the first trimester.

CLINICAL

Section 3 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

History

Polydactyly is the most common congenital digital anomaly of the hand and foot. It may appear in isolation or in association with other birth defects.

Physical

• Temtamy and McKusick⁶ classified polydactyly into preaxial, central, and postaxial types.
• • Preaxial polydactyly, the most common type, refers to the duplication of the first digit or ray.
  • Central polydactyly involves duplication of the second, third, or fourth digit or ray.
  • Postaxial polydactyly involves the fifth digit or ray. The terms radial, central, and ulnar have been proposed more recently as an alternative subclassification to describe polydactyly in the upper extremity.
• Similarly, the terms tibial, central, and fibular have been proposed to describe polydactyly in the lower extremity. Initially, polydactyly in the foot was believed to be a variant of the hand. Yet, findings show the association of hand and foot polydactyly to be uncommon.
• Even more rare is crossed polydactyly, where preaxial involvement of one extremity is coupled with postaxial involvement of the opposite end of the body.
• Synpolydactyly is the combination of syndactyly and polydactyly.⁷

Causes

See Pathophysiology.

DIFFERENTIALS

Section 4 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Other Problems to be Considered

Several dozen syndromes have been identified that include polydactyly as associated clinical manifestations. Among these are the following:

Acrocallosal syndrome
Basal cell nevus syndrome
Bardet-Biedl syndrome
Biemond syndrome
Ectrodactyly-ectodermal dysplasias-cleft lip/palate syndrome
Ellis van Creveld syndrome
Meckel Gruber syndrome
McKusick-Kaufman syndrome
Mirror hand deformity (ulnar dimelia)⁸
Mohr syndrome
Oral-facial-digital syndrome
Pallister-Hall syndrome
Rubinstein-Taybi syndrome
Short rib polydactyly
VATER association (vertebral [defects], [imperforate] anus, tracheoesophageal [fistula], radial and renal [dysplasia])

WORKUP

Section 5 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Lab Studies

• Because hand and foot polydactyly are associated with congenital defects in 23.4% of patients, genetic workup and thorough medical examination in these patients is recommended.
• • Polydactyly rarely is associated with congenital anomalies, except in recognizable syndromes. In one study by Castilla et al,⁹ trisomy 13, Meckel syndrome, and Down syndrome accounted for most cases of polydactyly.
  • Other associated syndromes include cerebellar vermis aplasia with features suggesting Meckel syndrome and Smith-Lemli-Opitz syndrome, Jeune syndrome, short rib-polydactyly syndromes (Saldino-Noonan syndrome and Majewski types), Ellis-van Creveld syndrome, acrocephalopolydactylous dysplasia, Bardet-Biedl (types 2 and 3), and trisomy (13-15). Down syndrome was associated strongly with duplication of the first digit.
• In addition, the incidence of postaxial polydactyly is less common in whites, suggesting that a systemic workup should be considered.

Imaging Studies

• Prenatal ultrasound^{10, 11}
• • Fetal finger buds can be seen using transvaginal ultrasound as early as 9 weeks and reliably by 13 weeks of pregnancy.
  • Once polydactyly is established, a thorough ultrasound evaluation, especially of the heart, nervous system, limbs, and kidneys, to identify an associated syndrome, such as Meckel Gruber syndrome and trisomy 13, should be performed.
  • Skeletal dysplasias also may cause polydactyly, such as short rib polydactyly. Follow-up ultrasound between 17-34 weeks with biometric profile is recommended to establish the diagnosis of isolated polydactyly. Skeletal dysplasias also may affect the hand, for instance, hitchhiker thumb in diastrophic dysplasia or polydactyly in short rib polydactyly. Isolated polydactyly has a good prognosis.
• Radiographs
• • Radiographs of the affected limb are recommended to show whether the rudimentary digit contains skeletal elements.
  • The degree of deviation of the digit and the size of the articulating metacarpal or metatarsal also may be helpful in surgical planning.

Histologic Findings

Rudimentary polydactyly, which may be a type of congenital traumatic neuroma, shows hyperkeratosis and acanthosis overlying many nerve bundles in the dermis. It may appear as a papule on the base of the ulnar side of the little finger. Abundant Merkel cells may appear at first and then disappear after the development of these nerve bundles, which form Meissner corpuscles in the dermal papillae and stain positively with S-100 protein.¹²

TREATMENT

Section 6 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Surgical Care

Surgical management depends greatly on the complexity of the deformity. Postaxial polydactyly of the foot most commonly is treated with surgical removal for cosmesis and shoe comfort. Waiting until age 9-12 months is advisable to decrease anesthesia risk.¹³ A related eMedicine article is Polydactyly of the Foot.

Consultations

A child with distal extremity anomalies experiences emotional stress.¹⁴ By age 3 years, the child has become aware of the anomaly. By age 7 years, the child has begun to experience the close scrutiny of his peers at school. For these reasons, as well as others, surgical correction should be initiated early in life. Needless to say, psychological support should be provided for patients and parents facing these challenges.

FOLLOW-UP

Section 7 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Complications

• Complications in the perioperative period include bleeding and anesthesia. Later, decreased function due to ligamentous laxity or contracture can occur.

MISCELLANEOUS

Section 8 of 9  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

Medical/Legal Pitfalls

• Failure to identify an associated syndrome

Special Concerns

• Posttraumatic amputation may occur.

REFERENCES

Section 9 of 9

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Follow-up
• Miscellaneous
• References

1. Hosalkar HS, Shah H, Gujar P, Kulkarni AD. Crossed polydactyly. J Postgrad Med. Jul-Sep 1999;45(3):90-2. [Medline].
2. Muragaki Y, Mundlos S, Upton J, Olsen BR. Altered growth and branching patterns in synpolydactyly caused by mutations in HOXD13. Science. Apr 26 1996;272(5261):548-51. [Medline].
3. Finley WH, Gustavson KH, Hall TM, Hurst DC, Barganier CM, Wiedmeyer JA. Birth defects surveillance: Jefferson County, Alabama, and Uppsala County, Sweden. South Med J. Apr 1994;87(4):440-5. [Medline].
4. Cohen MS. Thumb duplication. Hand Clin. Feb 1998;14(1):17-27. [Medline].
5. Hung L, Cheng JC, Bundoc R, Leung P. Thumb duplication at the metacarpophalangeal joint. Management and a new classification. Clin Orthop Relat Res. Feb 1996;31-41. [Medline].
6. Temtamy SA, McKusick VA. The genetics of hand malformations. Birth Defects Orig Artic Ser. 1978;14(3):i-xviii, 1-619. [Medline].
7. Malik S, Grzeschik KH. Synpolydactyly: clinical and molecular advances. Clin Genet. Feb 2008;73(2):113-20. [Medline].
8. Jafari D, Sharifi B. A variant of mirror hand. A case report. J Bone Joint Surg Br. Jan 2005;87(1):108-10. [Medline].
9. Castilla EE, Lugarinho R, da Graça Dutra M, Salgado LJ. Associated anomalies in individuals with polydactyly. Am J Med Genet. Dec 28 1998;80(5):459-65. [Medline].
10. Bromley B, Shipp TD, Benacerraf B. Isolated polydactyly: prenatal diagnosis and perinatal outcome. Prenat Diagn. Nov 2000;20(11):905-8. [Medline].
11. Zimmer EZ, Bronshtein M. Fetal polydactyly diagnosis during early pregnancy: clinical applications. Am J Obstet Gynecol. Sep 2000;183(3):755-8. [Medline].
12. Ban M, Kitajima Y. The number and distribution of Merkel cells in rudimentary polydactyly. Dermatology. 2001;202(1):31-4. [Medline].
13. Morley SE, Smith PJ. Polydactyly of the feet in children: suggestions for surgical management. Br J Plast Surg. Jan 2001;54(1):34-8. [Medline].
14. Eskandari MM, Oztuna V, Demirkan F. Late psychosocial effects of congenital hand anomaly. Hand Surg. Dec 2004;9(2):257-9. [Medline].
15. Al-Aithan B, Al-Blaihed L, Mahmoud S, Hassanain J, Al-Qattan MM. Thumb polydactyly with symphalangism. J Hand Surg [Br]. Aug 2005;30(4):346-9. [Medline].
16. Castilla EE, da Graca Dutra M, Lugarinho da Fonseca R, Paz JE. Hand and foot postaxial polydactyly: two different traits. Am J Med Genet. Nov 28 1997;73(1):48-54. [Medline].
17. Cavalcanti DP, Salomão MA. Dandy-Walker malformation with postaxial polydactyly: further evidence for autosomal recessive inheritance. Am J Med Genet. Jul 16 1999;85(2):183-4. [Medline].
18. Chiang H, Huang SC. Polydactyly of the foot: manifestations and treatment. J Formos Med Assoc. Mar 1997;96(3):194-8. [Medline].
19. Chung J, Nam IW, Ahn SK, Lee SH, Kim JG, Sung YO. Rudimentary polydactyly. J Dermatol. Jan 1994;21(1):54-5. [Medline].
20. Cummins H. Spontaneous amputation of human supernumerary digits: pedunculated postminimi. Am J Anat. 1932;51:381-416.
21. Graham TJ, Ress AM. Finger polydactyly. Hand Clin. Feb 1998;14(1):49-64. [Medline].
22. Hare PJ. Rudimentary polydactyly. Br J Dermatol. Nov 1954;66(11):402-8. [Medline].
23. Heras L, Barco J, Cohen A. Unusual complication of ligation of rudimentary ulnar digit. J Hand Surg [Br]. Dec 1999;24(6):750-1. [Medline].
24. Manske PR. Subclassification of polydactyly. Br J Plast Surg. Mar 1996;49(2):137. [Medline].
25. Sergi C, Adam S, Kahl P, Otto HF. Study of the malformation of ductal plate of the liver in Meckel syndrome and review of other syndromes presenting with this anomaly. Pediatr Dev Pathol. Nov-Dec 2000;3(6):568-83. [Medline].
26. Shapiro L, Juhlin EA, Brownstein MH. "Rudimentary polydactyly": an amputation neuroma. Arch Dermatol. Aug 1973;108(2):223-5. [Medline].

Article Last Updated: Jul 31, 2008