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Germline Pathogenic Variant in the APC Gene Suggestive of Gardner Syndrome in a Pony.
Abstract: A 12-year-old pony mare was presented for evaluation of dental disease and nasal discharge. At presentation, clinical signs included bilateral nasal discharge, cutaneous masses, and numerous hard enlargements involving the bones of the skull, maxilla, mandible, and cervical vertebrae. Oral exam revealed advanced dental disease with hard enlargements adjacent to and between numerous cheek teeth. Radiographs and computed tomography confirmed the presence of severe dental disease and proliferative bone lesions disseminated along the skull, hyoid apparatus, and cranial cervical vertebrae. The bony proliferations extended into the subcutis, nasal cavity, paranasal sinuses, orbits, cranial vault, and vertebral canal. Multifocal osteomas were considered the primary differential, and this was confirmed on biopsy of a bony mass. Due to the extent of the lesions and deterioration of the patient's quality of life, euthanasia was elected. On necropsy, multiple osteomas were present on the skull and to a lesser extent the cervical vertebrae. Additional abnormalities included multiple mucosal polyps in the small intestine, epidermal inclusion cysts, and adrenocortical adenomas. These findings resemble those seen in Gardner syndrome, a hereditary disease of people characterized by gastrointestinal polyps and extraintestinal manifestations, including osteomas, epidermoid cysts, adrenal tumors, and dental abnormalities. Historically, Gardner syndrome in people has been considered a separate condition from familial adenomatous polyposis (FAP). Gardner syndrome is now considered a variant of FAP associated with mutations in the adenomatous polyposis coli (APC) gene. Whole genome sequencing and variant discovery in the pony identified multiple unique variants, including a likely pathogenic single base pair insertion leading to a frameshift in APC (ENSECAP00000007276.1:p.Glu1527ArgfsTer9). While osteomas have been infrequently reported in horses, to the authors' knowledge, there have been no cases of Gardner syndrome described in equids. This case is highly suggestive of Gardner-like syndrome in an equid.
Copyright © 2026 J. Eric Martin et al. Case Reports in Veterinary Medicine published by John Wiley & Sons Ltd.
Publication Date: 2026-04-24 PubMed ID: 42038751PubMed Central: PMC13108242DOI: 10.1155/crve/1395580Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
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.
Overview
- A 12-year-old pony exhibited widespread bone growths and dental disease resembling Gardner syndrome, a genetic condition seen in humans.
- Genetic analysis revealed a pathogenic mutation in the APC gene, supporting a diagnosis of a Gardner syndrome-like disease in this pony.
Case Presentation and Clinical Findings
- The patient was a 12-year-old pony mare presenting with:
- Bilateral nasal discharge
- Multiple skin masses
- Numerous hard enlargements on skull bones, jaw (maxilla and mandible), and cervical vertebrae
- Advanced dental disease with hard nodules around cheek teeth observed during oral exam
- Diagnostic imaging (radiographs and computed tomography) showed:
- Severe dental disease
- Proliferative bony lesions covering skull, hyoid apparatus, and cervical vertebrae
- Bony growths extended into soft tissues including nasal cavity, sinuses, eye sockets, cranial vault, and vertebral canal
Diagnosis and Histopathology
- Primary differential diagnosis was multifocal osteomas (benign bone tumors).
- Biopsy of a bone mass confirmed osteomas histologically.
- Due to severity and negative impact on quality of life, euthanasia was chosen.
Necropsy Findings
- Multiple osteomas present on the skull and cervical vertebrae.
- Additional abnormalities detected included:
- Multiple mucosal polyps in the small intestine
- Epidermal inclusion cysts (benign skin cysts)
- Adrenocortical adenomas (benign adrenal gland tumors)
Comparison to Gardner Syndrome
- The pony’s clinical signs resemble Gardner syndrome, a hereditary human disorder characterized by:
- Gastrointestinal polyps
- Osteomas and other bone tumors
- Skin cysts
- Adrenal tumors
- Dental abnormalities
- In humans, Gardner syndrome is now considered a variant of familial adenomatous polyposis (FAP).
- Both conditions are linked to mutations in the APC gene, which encodes the adenomatous polyposis coli protein responsible for regulating cell growth.
Genetic Analysis
- Whole genome sequencing of the pony identified multiple unique gene variants.
- A pathogenic variant was discovered: a single base pair insertion in the APC gene causing a frameshift mutation (p.Glu1527ArgfsTer9).
- This mutation likely disrupts APC gene function, consistent with the development of osteomas and polyps as seen in Gardner syndrome.
Significance and Novelty
- Osteomas have been rarely reported in horses, but there are no previous documented cases of Gardner syndrome or similar genetic syndromes in equids.
- This is the first reported case highly suggestive of Gardner-like syndrome in a pony, expanding the spectrum of inherited diseases affecting horses.
- Identification of the APC mutation suggests a genetic basis mirroring human disease, offering potential insights into veterinary and comparative pathology.
Cite This Article
APA
Martin JE, Hecht S, Craig L, Durward-Akhurst SA, Marlowe JL, Hines MT.
(2026).
Germline Pathogenic Variant in the APC Gene Suggestive of Gardner Syndrome in a Pony.
Case Rep Vet Med, 2026, 1395580.
https://doi.org/10.1155/crve/1395580 Publication
Researcher Affiliations
- University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, USA, tennessee.edu.
- University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, USA, tennessee.edu.
- University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, USA, tennessee.edu.
- Department of Veterinary Clinical Sciences, University of Minnesota, St. Paul, Minnesota, USA, umn.edu.
- Department of Veterinary Clinical Sciences, University of Minnesota, St. Paul, Minnesota, USA, umn.edu.
- University of Tennessee College of Veterinary Medicine, Knoxville, Tennessee, USA, tennessee.edu.
Conflict of Interest Statement
The authors declare no conflicts of interest.
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