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PubMed This is a summary of 13 peer-reviewed journal articles Updated
Pediatrics

Understanding Your Baby's Extra Digit: Postaxial Polydactyly Type B

At a Glance

Postaxial polydactyly type B is a common, harmless condition where a baby is born with a soft-tissue extra finger or toe on the pinky side. It rarely indicates any underlying health issues and can be safely removed through a minor surgical excision.

Finding out your baby has an extra finger or toe can be an unexpected and overwhelming experience. However, Postaxial Polydactyly Type B is a very common, benign condition [1][2]. In the vast majority of cases, this is an isolated finding, meaning your baby is otherwise perfectly healthy and the extra digit has no impact on their overall development [3][1].

Defining Postaxial Polydactyly Type B

The term postaxial refers to the location: the extra digit is on the “pinky” side of the hand or the “little toe” side of the foot [2]. Type B describes the specific form of this extra digit [4]:

  • Appearance: It is typically a small, soft, skin-covered appendage [2].
  • Structure: It is often pedunculated, meaning it hangs from the hand or foot by a thin stalk of tissue rather than a wide base [2][1].
  • Composition: Unlike “Type A” polydactyly, which is a fully formed finger with bone and joints, Type B contains little to no bony elements [4][1].

Understanding the Cause and Inheritance

This condition is one of the most frequent variations seen in newborns. It is particularly common in certain ethnic groups, including those of African descent, where it often appears as an isolated trait [5][6].

In many families, this trait is simply inherited. This means that if a parent carries the genetic trait for an extra digit, there is a chance of passing it on to their child. However, a parent might carry the gene without having had an extra digit themselves [1][2]. Researchers have identified several genes that play a role in how fingers and toes form during development [7][8].

Is it Part of a Larger Syndrome?

One of the most reassuring facts about Type B polydactyly is that it is rarely associated with other medical issues [3].

  • Isolated vs. Syndromic: Most cases of Type B are “isolated,” meaning the extra digit is the only unusual finding [1].
  • Comparison: While Type A (the fully formed extra finger) is more frequently linked to genetic syndromes, Type B is much more likely to be a simple, benign variation [3][1].

Your pediatrician will perform a thorough physical exam to confirm this is an isolated finding. They may look at your baby’s heart, facial features, and other growth patterns just to be certain [9][10].

Next Steps for Your Family

Because Type B digits are usually just soft tissue attached by a thin stalk, they are generally easy to address. Options typically include suture ligation (tying it off) or surgical excision (a minor removal procedure) [11][12].

While “tying it off” was common in the past, modern pediatric guidelines increasingly favor surgical excision to avoid painful complications and ensure a clean result [12][13]. You can read a detailed breakdown in our section on Treatment Options and learn why imaging is important in the Diagnostic Process section.

Common questions in this guide

Is an extra finger or toe a sign of a larger health problem?
In the vast majority of cases, postaxial polydactyly type B is an isolated finding. This means the extra digit is the only unusual trait and your baby is likely otherwise perfectly healthy.
What is the difference between Type A and Type B polydactyly?
Type A polydactyly is a fully formed extra digit that contains bone and joints. Type B is a soft, skin-covered appendage that usually has little to no bone and hangs from the hand or foot by a thin stalk.
How is postaxial polydactyly type B treated?
Because Type B digits are usually soft tissue on a thin stalk, they can be removed through suture ligation (tying it off) or a minor surgical excision. Modern pediatric guidelines increasingly favor surgical excision to avoid complications and ensure a clean result.
Will my child need to see a geneticist for an extra digit?
Most cases are simple, benign variations. Your pediatrician will perform a thorough physical exam, and genetic consultation is usually only recommended if other unusual physical features are present.
Is an extra digit an inherited trait?
Yes, in many families this trait is inherited. If a parent carries the genetic trait, they can pass it to their child, even if the parent was not born with an extra digit themselves.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Based on your physical examination, is my child's extra digit purely soft tissue, or does it feel like it contains bone?
  2. 2.Does my child have any other physical findings that would suggest this is part of a larger syndrome, or is this an isolated trait?
  3. 3.Should we consider genetic testing or a consultation with a geneticist, or is that unnecessary given the exam?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (13)
  1. 1

    Polydactyly, postaxial, type B.

    Holmes LB, Nasri H, Hunt AT, et al.

    Birth defects research 2018; (110(2)):134-141 doi:10.1002/bdr2.1184.

    PMID: 29377639
  2. 2

    Isolated postaxial polydactyly: Epidemiologic characteristics from a multicenter birth defects study.

    Ortiz-Cruz G, Luna-Muñoz L, Arteaga-Vázquez J, Mutchinick OM

    American journal of medical genetics. Part A 2019; (179(8)):1432-1441 doi:10.1002/ajmg.a.61193.

    PMID: 31091006
  3. 3

    Predictors of Syndromic Association in Ulnar Polydactyly: Analysis of a Multicenter Congenital Hand Differences Registry in the United States.

    McQuillan T, Antonellis H, Wall L, et al.

    The Journal of hand surgery 2026; (51(3)):292-300 doi:10.1016/j.jhsa.2025.03.019.

    PMID: 40377505
  4. 4

    A novel missense mutation in TFAP2B associated with Char syndrome and central diabetes insipidus.

    Edward HL, D'Gama AM, Wojcik MH, et al.

    American journal of medical genetics. Part A 2019; (179(7)):1299-1303 doi:10.1002/ajmg.a.61150.

    PMID: 31012281
  5. 5

    New Insights into Host Genetic Ancestry as a Risk Factor for Dengue Disease.

    Barratt-Boyes SM, Castanha PMS

    DNA and cell biology 2025; (44(12)):642-646 doi:10.1177/10445498251379003.

    PMID: 40982307
  6. 6

    Advancing neurogenetics in Africa: past achievements, current developments and shaping the future.

    Landouré G, Yalcouyé A, Diarra S, et al.

    Nature reviews. Neurology 2025; (21(7)):383-393 doi:10.1038/s41582-025-01098-3.

    PMID: 40410580
  7. 7

    GLI1 inactivation is associated with developmental phenotypes overlapping with Ellis-van Creveld syndrome.

    Palencia-Campos A, Ullah A, Nevado J, et al.

    Human molecular genetics 2017; (26(23)):4556-4571 doi:10.1093/hmg/ddx335.

    PMID: 28973407
  8. 8

    Heterozygous pathogenic variants in GLI1 are a common finding in isolated postaxial polydactyly A/B.

    Palencia-Campos A, Martínez-Fernández ML, Altunoglu U, et al.

    Human mutation 2020; (41(1)):265-276 doi:10.1002/humu.23921.

    PMID: 31549748
  9. 9

    Postaxial polydactyly: A case report highlighting genetic context, epidemiological trends, and management options.

    Yared G, Ghazal K, Younis A, et al.

    SAGE open medical case reports 2024; (12()):2050313X241282215 doi:10.1177/2050313X241282215.

    PMID: 39314219
  10. 10

    Third case of Bardet-Biedl syndrome caused by a biallelic variant predicted to affect splicing of IFT74.

    Mardy AH, Hodoglugil U, Yip T, Slavotinek AM

    Clinical genetics 2021; (100(1)):93-99 doi:10.1111/cge.13962.

    PMID: 33748949
  11. 11

    Long-Term Outcomes After Treatment for Type B Ulnar Polydactyly.

    Goebel GJ, Dawson S, Loewenstein SN, Adkinson JM

    Journal of pediatric orthopedics 2022; (42(5)):e466-e469 doi:10.1097/BPO.0000000000002106.

    PMID: 35220338
  12. 12

    Local Anesthesia Alone for Postaxial Polydactyly Surgery in Infants.

    Bjorklund KA, O'Brien M

    Hand (New York, N.Y.) 2022; (17(6)):1286-1291 doi:10.1177/1558944721994255.

    PMID: 33631987
  13. 13

    Office-Based Post-Axial Polydactyly Excision in Neonates, Infants, and Children.

    Carpenter CL, Cuellar TA, Friel MT

    Plastic and reconstructive surgery 2016; (137(2)):564-568 doi:10.1097/01.prs.0000475787.67693.e7.

    PMID: 26818291

This page provides educational information about postaxial polydactyly type B. It is not a substitute for professional medical advice. Always consult your pediatrician or pediatric surgeon for an accurate diagnosis and treatment plan for your child.

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