Aniridia in Two Related Tennessee Walking Horses

Karen A Mccormick,Kimberly M Newkirk,Daniel Ward

doi:10.1155/2013/703732

Karen A Mccormick, Kimberly M Newkirk + Show 1 more

Open Access

https://doi.org/10.1155/2013/703732

Copy DOI

Abstract

Aniridia in horses is rare and has previously been reported to be genetically transmitted in Belgian horses and Quarter horses. This paper describes the defect in 2 related Tennessee Walking horses, with special reference to new findings regarding the molecular genetics of ocular development and how they might relate to equine aniridia. In addition to aniridia, these 2 horses possessed additional ocular abnormalities including cataracts and dermoid lesions. Euthanasia was elected, and the eyes were examined histologically. Iris hypoplasia, atypical dermoids, and cataracts were confirmed in both horses. Due to the heritability of aniridia in horses, breeding of affected animals is not recommended.

Highlights

Aniridia is a rare condition marked by partial or complete absence of the iris
In Belgian horses [6] and Quarter horses [7], the defect has been reported to be genetically transmitted as an autosomal dominant trait, but at least one case in a Swedish Warmblood was not dominantly inherited [8]
Like many instances of aniridia, form during foetal development, and our understanding of the molecular genetics of ocular development has improved since the last case report of aniridia in horses [8]

Summary

Introduction

Aniridia is a rare condition marked by partial or complete absence of the iris. This condition has been reported in horses [6,7,8,9,10,11], cattle [1], laboratory animals [2, 3], and humans [4, 5]. Like many instances of aniridia, form during foetal development, and our understanding of the molecular genetics of ocular development has improved since the last case report of aniridia in horses [8]. The purpose of this report is to describe the clinical and histologic features of aniridia in 2 related Tennessee Walking horses, especially considering “new” information about the genetics of ocular involvement

Case Presentation

Histopathology

Discussion