Peer-reviewed veterinary case report
Skeletal atavism in a miniature horse.
- Journal:
- Veterinary radiology & ultrasound : the official journal of the American College of Veterinary Radiology and the International Veterinary Radiology Association
- Year:
- 2004
- Authors:
- Tyson, Reid et al.
- Affiliation:
- Veterinary Specialists Center · United States
- Species:
- horse
Plain-English summary
An 8-month-old female miniature horse was brought in because she had serious problems with her legs, which were twisting and bending in unusual ways. X-rays showed that she had complete ulna and fibula bones, which are traits not typically seen in modern horses but were present in their distant ancestors. This condition is called atavism, where old traits reappear after being absent for a long time. The horse also had a condition called bilateral osteochondritis dissecans, which affects the knee joint. This case is notable because it's the first time these specific bone traits have been reported in a miniature horse.
Abstract
An 8-month-old miniature horse filly was presented for evaluation of severe rotational and angular limb deformities of the thoracic and pelvic limbs. On radiographic examination, complete ulnas and fibulas were identified. These findings are consistent with a condition previously described as a form of atavism. The term atavism is used to describe the reappearance of a trait or character that was seen in all earlier evolutionary specimens of a particular species, but has not been seen in recent ancestors. The atavistic traits of complete ulnas and fibulas have previously been described in Welsh and Shetland Ponies, all of which had severe rotational and angular limb deformities. In this horse, bilateral osteochondritis dissecans of the medial trochlear ridge of the talii were also identified. To the authors' knowledge, this is the first report of the atavistic traits of complete ulnas and fibulas seen in the miniature horse.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/15373256/