Glycogen-branching enzyme deficiency
Glycogen-branching enzyme deficiency is a genetic disease affecting horses, especially American Quarter Horses and related breeds.
Diagnosis, symptoms, and prognosis
Lacking an enzyme necessary for storing glycogen, the horse's brain, heart muscle, and skeletal muscles cannot function, leading to rapid death. This condition may be diagnosed with a muscle biopsy. Most foals with glycogen-branching enzyme deficiency (GBED) are aborted, usually in the second trimester, or stillborn,[1] and those that survive live only for a few months. Symptoms include general weakness, contracted tendons, seizures, cardiac arrest, and sudden death. No treatment is known.
Causes
The disease occurs in foals that are homozygous for the lethal GBED allele, meaning both parents must be heterozygous for the allele. A blood test for this allele was developed by the University of Minnesota College of Veterinary Medicine and as of 2005[update] is licensed to the UC Davis Veterinary Genetics Laboratory. Using this, breeders can avoid crosses that could produce GBED foals, and eventually selectively breed it out. Carrier frequency has been estimated at 7.1% in the Quarter Horse, 8.3% in the Paint Horse, and as high as 26% in Western Pleasure horses.[2]
This genetic disease has been linked to the foundation Quarter Horse sire King P-234.
See also
Glycogen storage disease type IV
References
"Testing for Genetic Diseases" Equus 353, pp 40-41.
- ^ Valberg SJ, Ward TL, Rush B, Kinde H, Hiraragi H, et al. 2001. Glycogen branching enzyme deficiency in Quarter Horse foals. J. Vet. Intern. Med. 15:572–80
- ^ Wagner ML, Valberg SJ, Ames EG, Bauer MM, Wiseman JA, et al. 2006. Allele frequency and likely impact of the glycogen branching enzyme deficiency gene in Quarter Horse and Paint Horse populations. J. Vet. Intern. Med. 20:1207–11