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Home / Equine Research Bank / Equine Vet J / Inherited non-syndromic polydactyly in a Berber and Arabian-...
Equine veterinary journal2025; doi: 10.1111/evj.14472

Inherited non-syndromic polydactyly in a Berber and Arabian-Berber horse family.

Abstract: Supernumerary digits, or polydactyly, have been described in various species including humans, wild and domestic animals. In horses, it represents the most common congenital limb malformation, which has only been described in isolated cases or nuclear families. Molecular aetiology has not been reported. Objective: To characterise the phenotype of a non-syndromic pre-axial polydactyly in a horse family and to decipher the inheritance pattern. Methods: Retrospective study. Methods: Forty-three members of the family including a previously reported polydactyl case were recruited. Available clinical and radiographical findings from the initial case and its family members were summarised and karyotypic examinations of the horses were performed. Results: On clinical examination, eight horses (including the previously reported case) had one or two supernumerary digits on their forelimbs and one additional case was diagnosed using radiography. Additional digits were located on the medial side of the forelimbs in all nine polydactyl horses. Radiography highlighted variable expression of the defect, which was either unilateral or bilateral. Variations were observed in the number of supernumerary phalanges, the level of development of a rudimentary metacarpal bone, the individualisation of a supernumerary digit and the existence of a rudimentary hoof. All nine affected horses were related to a single stallion. Pedigree analysis revealed that the most likely inheritance pattern was autosomal dominant with incomplete penetrance and variable expressivity. A more complex mode could not be ruled out. Conclusions: Restricted recruitment of the family members due to confidentiality constraints and to international dispersal of the relatives, quality of radiographs. Conclusions: We describe an equine preaxial polydactyly in a Berber and Arabian-Berber family most likely with autosomal dominant inheritance with incomplete penetrance. This is the first description of an inherited non-syndromic polydactyly in horses. Background: Des doigts surnuméraires, ou polydactylie, ont été décrit chez plusieurs espèces incluant l'homme, de même que les animaux domestiques et sauvages. Chez le cheval, il s'agit de la malformation congénitale des membres la plus fréquente, ayant été décrite dans des cas isolés seulement ou au sein de familles nucléaires. Une étiologie moléculaire n'a pas encore été rapportée. Objective: Caractériser le phénotype d'une polydactylie non syndromique de type préaxial au sein d'une famille équine et identifier un mode de transmission. TYPE D'ÉTUDE: Étude rétrospective. MÉTHODES: À partir d'un étalon Barbe polydactyle présenté à l'École Vétérinaire d'Alfort (France), 43 chevaux (8 polydactyles, 35 non‐polydactyles) de sa famille ont été recruté. Des examens cliniques, radiographiques et karyotypiques de certains chevaux de cette famille ont été faits. RÉSULTATS: Une famille équine Barde et Arabe croisé Barbe avec polydactylie préaxiale non syndromique a été identifiée. À l'examen clinique, huit chevaux ont montré un ou deux doigts surnuméraires au niveau des membres thoraciques et une jument a été diagnostiquée par radiographie. Les doigts additionnels étaient localisés du côté médial des membres thoraciques chez les 9 chevaux polydactyles. L'analyse radiographique a identifié une expression variable de ce défaut, soit unilatéral ou bilatéral. Des variations ont été observées quant au nombre de phalanges surnuméraires, pour le développement des os métacarpiens, pour l'individualisation d'un doigt surnuméraires et l'existence d'un sabot rudimentaire. L'ensemble des neuf chevaux étaient reliés au même étalon. L'analyse généalogique a révélé que le mode de transmission le plus probable était autosomique dominant avec une pénétrance incomplète et une expressivité variable. Une mode de transmission plus complexe ne peut être exclu. Unassigned: Recrutement restreint des membres de la famille due à des contraintes de confidentialité et des membres de la famille situés dans d'autres pays; qualité des radiographies. Conclusions: Nous avons découvert une polydactylie équine préaxiale chez une famille Barbe et Arabe croisé Barbe ayant le plus probablement un mode de transmission autosomique dominant avec pénétrance incomplète. À ce que nous sachions, ceci représente la toute première description de polydactylie non syndromique héréditaire chez le cheval.
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Publication Date: 2025-01-24 PubMed ID: 39853805DOI: 10.1111/evj.14472Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research study investigates the skeletal malformation known as polydactyly – an abnormal development resulting in extra digits – in a horse family of Berber and Arabian-Berber breeds. The study aims to characterize this non-syndromic polydactyly and understand its inheritance pattern. Findings suggest that the malformation is likely inherited in an autosomal dominant manner but with incomplete penetrance, meaning not all horses carrying the gene express the trait.

Methods and Results

  • The researchers conducted a retrospective study involving 43 members of a horse family, including one previously reported polydactyl case.
  • The clinical and radiographical findings were compiled to further understand the phenotype of the disease.
  • Of the horses studied, eight were found to have one or two supernumerary (extra) digits on their forelimbs. One additional case was diagnosed through radiography, taking the total to nine affected horses.
  • All of these polydactyl horses were related to a single stallion, suggesting a genetic contribution to the disease.
  • The radiographs highlighted the existence of variable expressions of the defect, with variations evident in the number, development, and individualization of the supernumerary phalanges, as well as the existence of a rudimentary hoof. These could be either unilateral (one side) or bilateral (both sides).

Inheritance Pattern

  • The researchers also analyzed the pedigree of the research subjects and observed that the most likely inheritance pattern of this malformation was autosomal dominant. This means the trait can be passed on by one affected parent and could manifest in the offspring even if the other parent does not carry the gene.
  • However, the effect was seen with incomplete penetrance, meaning that not every horse carrying the gene exhibited the trait. The severity of the trait’s expression also varied among the affected horses, again pointing to variable expressivity.
  • The study acknowledged that a more complex inheritance pattern could not be ruled out due to the observed variability in the expression of the trait and the number of affected horses.

Limitations and Conclusions

  • One of the limitations of the study was the restricted recruitment of the family members due to confidentiality constraints and dissemination of the family members in different locations.
  • The quality of the radiographs could also be a limiting factor as this might affect the detailed examination of the defect.
  • Despite these constraints, the study provides the first description of inherited non-syndromic polydactyly in horses, specifically in a Berber and Arabian-Berber family. The likely autosomal dominant inheritance pattern with incomplete penetrance is an important observation for future research and clinical practice.

Cite This Article

APA
Baville E, Carstanjen B, Thomas-Cancian A, Calgaro A, Bonnet N, Tiret L, Gache V, Abitbol M. (2025). Inherited non-syndromic polydactyly in a Berber and Arabian-Berber horse family. Equine Vet J. https://doi.org/10.1111/evj.14472

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Baville, Ella
  • Université de Lyon, VetAgro Sup, Marcy l'Etoile, France.
Carstanjen, Bianca
  • Pferdepraxis, Weilheim, Germany.
Thomas-Cancian, Aurélie
  • Université de Lyon, VetAgro Sup, Marcy l'Etoile, France.
Calgaro, Anne
  • Université de Toulouse, Genphyse, INRAE, Ecole Nationale Vétérinaire de Toulouse, Toulouse, France.
Bonnet, Nathale
  • Université de Toulouse, Genphyse, INRAE, Ecole Nationale Vétérinaire de Toulouse, Toulouse, France.
Tiret, Laurent
  • Université Paris-Est Créteil, INSERM, EFS, EnvA, IMRB Team Relaix, Ecole Nationale Vétérinaire d'Alfort, Maisons-Alfort, France.
Gache, Vincent
  • Université de Lyon, UCBL1 CNRS UMR5261, INSERM U1315, Institut NeuroMyoGene INMG-PNMG Team MNCA, Lyon, France.
Abitbol, Marie
  • Université de Lyon, VetAgro Sup, Marcy l'Etoile, France.
  • Université de Lyon, UCBL1 CNRS UMR5261, INSERM U1315, Institut NeuroMyoGene INMG-PNMG Team MNCA, Lyon, France.

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