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PubMed This is a summary of 18 peer-reviewed journal articles Updated
Medical Genetics

Genetics and Associated Syndromes

At a Glance

While most children born with Postaxial Polydactyly Type A (PAPA) live completely healthy lives, the extra digit can sometimes be linked to a genetic syndrome. Doctors proactively screen the heart and kidneys because the same genes that form limbs also guide organ development.

When a child is born with Postaxial Polydactyly Type A (PAPA), doctors often recommend a visit to a geneticist (a doctor who specializes in genes and heredity). While an extra digit may seem like a simple physical difference, it can sometimes be a “clue” to how the rest of the body developed [1][2].

Putting the Risk in Perspective

Hearing the word “syndrome” is terrifying for any parent. It is vital to know that the vast majority of children born with an extra digit go on to live completely normal, healthy lives. The severe syndromes mentioned below are rare possibilities. Doctors screen for them out of an abundance of caution—to be absolutely certain your child is safe—not because they expect a devastating outcome [3][2].

Isolated vs. Syndromic: What Is the Difference?

The first step in a genetic evaluation is determining if the extra digit is isolated or syndromic.

  • Isolated (Non-Syndromic): This means the extra finger or toe is the only medical finding. The rest of the child’s body and organs are developing typically [3][4].
  • Syndromic: This means the extra digit is part of a syndrome—a group of health features that often occur together because they share a single genetic cause [5][6].

Because Type A digits are “fully formed” with bone and joints, they carry a higher risk than smaller “skin-tag” types (Type B) of being associated with a syndrome [1][7].

The Role of the “Cilia” (Ciliopathies)

Many syndromes associated with extra digits involve primary cilia. Imagine every cell in the body has a tiny, hair-like “antenna” on its surface. These antennae, called cilia, help cells “talk” to each other and send signals that tell the body how to grow [8][9].

When these antennae don’t work correctly, it is called a ciliopathy [8]. Because cilia are found all over the body—in the heart, kidneys, eyes, and limbs—a problem with them can cause multiple features, such as:

  • Extra digits (polydactyly) [8].
  • Kidney issues, as cilia are vital for kidney function [10].
  • Vision or heart differences [10][11].

Common Genetic Associations

Several specific genes and rare syndromes are well-known to doctors when evaluating PAPA:

  • GLI3 Mutations: The GLI3 gene is like a “master switch” for limb and organ growth [12][13]. Conditions linked to this switch (like Greig Cephalopolysyndactyly or Pallister-Hall) are passed down in an autosomal dominant pattern, meaning only one parent needs to pass the gene [14][15].
  • Bardet-Biedl Syndrome (BBS) & Ellis-van Creveld Syndrome (EvC): These are rare, autosomal recessive conditions. Both parents must be silent carriers. These syndromes can involve the kidneys, vision, or heart, in addition to extra digits [10][16][17].

Why the Systemic Check Is Important

Your doctor isn’t looking for problems to cause worry; they are performing a systemic check to be proactive [2]. Because the same genes that build fingers also help build the heart and kidneys, routine screenings like a renal (kidney) ultrasound or an echocardiogram (heart ultrasound) ensure every part of your child is working exactly as it should [2][18].

Common questions in this guide

Is an extra finger or toe always a sign of a severe genetic syndrome?
No. The vast majority of children born with an extra digit have an isolated finding and live completely normal, healthy lives. Doctors screen for syndromes out of an abundance of caution, not because they expect a severe problem.
What is the difference between isolated and syndromic polydactyly?
Isolated polydactyly means the extra digit is the only medical difference, and the rest of the body is developing normally. Syndromic polydactyly means the extra finger or toe is part of a larger group of health features caused by a single genetic change.
Why does my baby need a kidney or heart ultrasound just for having an extra digit?
The genes that control how fingers and toes grow also help build internal organs. Doctors perform routine ultrasounds of the kidneys and heart simply to be proactive and ensure every part of your child is working exactly as it should.
What is a ciliopathy?
Ciliopathies are conditions caused by problems with primary cilia, which are tiny hair-like structures on cells that help them communicate. Because cilia are found throughout the body, an issue with them can cause extra digits alongside kidney, vision, or heart differences.
What is the role of the GLI3 gene in extra digits?
The GLI3 gene acts as a master switch for limb and organ growth. Mutations in this gene are associated with certain syndromes that feature extra digits, and this gene can be passed down from just one parent.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Is my child's extra digit an isolated finding, or are there other subtle physical signs that might point to a syndrome?
  2. 2.Why are we specifically checking the heart and kidneys, and what tests (like ultrasound) will be used?
  3. 3.Given my family history, is this more likely to follow an autosomal dominant or autosomal recessive inheritance pattern?

Questions For You

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References

References (18)
  1. 1

    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
  2. 2

    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
  3. 3

    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
  4. 4

    A Novel Frameshift Mutation of GLI3 Causes Isolated Postaxial Polydactyly.

    Ni F, Han G, Guo R, et al.

    Annals of plastic surgery 2019; (82(5)):570-573 doi:10.1097/SAP.0000000000001685.

    PMID: 30562203
  5. 5

    Two Nonsense GLI3 Variants Are Identified in Two Chinese Families With Polydactyly.

    Qi Y, Liu K, Wei Y, et al.

    Molecular genetics & genomic medicine 2025; (13(3)):e70088 doi:10.1002/mgg3.70088.

    PMID: 40052367
  6. 6

    Exome sequencing revealed a splice site variant in the IQCE gene underlying post-axial polydactyly type A restricted to lower limb.

    Umair M, Shah K, Alhaddad B, et al.

    European journal of human genetics : EJHG 2017; (25(8)):960-965 doi:10.1038/ejhg.2017.83.

    PMID: 28488682
  7. 7

    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
  8. 8

    Renal cystic disease and associated ciliopathies.

    Kagan KO, Dufke A, Gembruch U

    Current opinion in obstetrics & gynecology 2017; (29(2)):85-94 doi:10.1097/GCO.0000000000000348.

    PMID: 28151755
  9. 9

    The relevance of primary cilia in neurological disorders.

    Serpieri V, D'Abrusco F, Valente EM

    The Lancet. Neurology 2025; (24(9)):763-775 doi:10.1016/S1474-4422(25)00226-1.

    PMID: 40706604
  10. 10

    Multiple genetic mutations implicate spectrum of phenotypes in Bardet-Biedl syndrome.

    Chakrabarty S, Savantre SB, Ramachandra Bhat C, Satyamoorthy K

    Gene 2020; (725()):144164 doi:10.1016/j.gene.2019.144164.

    PMID: 31639430
  11. 11

    Truncation and microdeletion of EVC/EVC2 with missense mutation of EFCAB7 in Ellis-van Creveld syndrome.

    Nguyen TQ, Saitoh M, Trinh HT, et al.

    Congenital anomalies 2016; (56(5)):209-16 doi:10.1111/cga.12155.

    PMID: 26748586
  12. 12

    Novel GLI3 variant causing overlapped Greig cephalopolysyndactyly syndrome (GCPS) and Pallister-Hall syndrome (PHS) phenotype with agenesis of gallbladder and pancreas.

    Ito S, Kitazawa R, Haraguchi R, et al.

    Diagnostic pathology 2018; (13(1)):1 doi:10.1186/s13000-017-0682-8.

    PMID: 29368652
  13. 13

    Greig Cephalopolysyndactyly Syndrome: Phenotypic Variability Associated with Variants in Two Different Domains of GLI3.

    Khan H, , Ahmed S, et al.

    Klinische Padiatrie 2021; (233(2)):53-58 doi:10.1055/a-1223-2489.

    PMID: 33339065
  14. 14

    Autistic symptoms in Greig cephalopolysyndactyly syndrome: a family case report.

    Siracusano M, Riccioni A, Baratta A, et al.

    Journal of medical case reports 2019; (13(1)):100 doi:10.1186/s13256-019-2043-6.

    PMID: 31010437
  15. 15

    A GLI3 variant leading to polydactyly in heterozygotes and Pallister-Hall-like syndrome in a homozygote.

    Kariminejad A, Ghaderi-Sohi S, Keshavarz E, et al.

    Clinical genetics 2020; (97(6)):915-919 doi:10.1111/cge.13730.

    PMID: 32112393
  16. 16

    Bardet-Biedl Syndrome Presenting With Bifid Epiglottis: A Case Report and Review of Literature.

    Saif SA, Alzaidi SS, Alghamdi AF, et al.

    Cureus 2023; (15(4)):e37849 doi:10.7759/cureus.37849.

    PMID: 37214040
  17. 17

    Case Report of a Novel EVC Gene Mutation in Ellis-van Creveld Syndrome: Implications for Pediatric Dental Management.

    Shariati M, Tavassoli-Hojjati S, Hoseini AP, Jadidi H

    Case reports in dentistry 2025; (2025()):6628305 doi:10.1155/crid/6628305.

    PMID: 41438176
  18. 18

    Renal involvement as a potential feature of pyogenic arthritis, pyoderma gangrenosum, and acne syndrome with E250K mutation of PSTPIP1 gene.

    Zhao R, Novice T, Konda S

    JAAD case reports 2023; (32()):48-51 doi:10.1016/j.jdcr.2022.11.030.

    PMID: 36660269

This information about the genetics of Postaxial Polydactyly Type A is for educational purposes only. Always consult a pediatric geneticist or your child's pediatrician for formal genetic screening and medical advice.

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