eMedicine Specialties > Dermatology > Pediatric Diseases

Supernumerary Digit

Author: Carter G Abel, MD, Clinical Assistant Attending, Department of Dermatology, New York Presbyterian Hospital
Coauthor(s): Denise M McCarthy, MD, Associate Professor, Department of Radiology, Morristown Memorial Hospital
Contributor Information and Disclosures

Updated: Jul 31, 2008

Introduction

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

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.

More on Supernumerary Digit

Overview: Supernumerary Digit
Differential Diagnoses & Workup: Supernumerary Digit
Treatment & Medication: Supernumerary Digit
Follow-up: Supernumerary Digit
References
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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].

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Further Reading

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Keywords

rudimentary polydactyly, digital duplication, hand anomaly, synpolydactyly

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Contributor Information and Disclosures

Author

Carter G Abel, MD, Clinical Assistant Attending, Department of Dermatology, New York Presbyterian Hospital
Carter G Abel, MD is a member of the following medical societies: American Academy of Dermatology, American College of Mohs Micrographic Surgery and Cutaneous Oncology, American Society for Dermatologic Surgery, and Medical Society of New Jersey
Disclosure: Nothing to disclose.

Coauthor(s)

Denise M McCarthy, MD, Associate Professor, Department of Radiology, Morristown Memorial Hospital
Denise M McCarthy, MD is a member of the following medical societies: American Association for Women Radiologists, American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Disclosure: Nothing to disclose.

Medical Editor

Albert C Yan, MD, Section Chief, Associate Professor, Department of Pediatrics, Section of Dermatology, Children's Hospital of Philadelphia and University of Pennsylvania
Albert C Yan, MD is a member of the following medical societies: American Academy of Dermatology, American Academy of Pediatrics, Society for Investigative Dermatology, and Society for Pediatric Dermatology
Disclosure: Nothing to disclose.

Pharmacy Editor

Richard P Vinson, MD, Assistant Clinical Professor, Department of Dermatology, Texas Tech University School of Medicine; Consulting Staff, Mountain View Dermatology, PA
Richard P Vinson, MD is a member of the following medical societies: American Academy of Dermatology, Association of Military Dermatologists, Texas Dermatological Society, and Texas Medical Association
Disclosure: Nothing to disclose.

Managing Editor

Robert A Schwartz, MD, MPH, Professor and Head of Dermatology, Professor of Medicine, Professor of Pediatrics, Professor of Pathology, Professor of Preventive Medicine and Community Health, UMDNJ-New Jersey Medical School
Robert A Schwartz, MD, MPH is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American College of Physicians, and Sigma Xi
Disclosure: Nothing to disclose.

CME Editor

Glen H Crawford, MD, Assistant Clinical Professor, Department of Dermatology, University of Pennsylvania School of Medicine; Chief, Division of Dermatology, The Pennsylvania Hospital
Glen H Crawford, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Dermatology, American Medical Association, Phi Beta Kappa, and Society of USAF Flight Surgeons
Disclosure: Nothing to disclose.

Chief Editor

Dirk M Elston, MD, Director, Department of Dermatology, Geisinger Medical Center
Dirk M Elston, MD is a member of the following medical societies: American Academy of Dermatology
Disclosure: Nothing to disclose.

 
 
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