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Glycogen Storage Disease IV (GSD IV/GBED)


 → Lethal energy deficiency in muscles and organs.

Instructions for ordering:

  1. Enter the information of the first horse for which you want to order the test
  2. Add to cart
  3. Go to cart to check out, or
  4. Enter the information for a second horse
  5. For sample collection follow the instructions here.
  6. You can use this template to send in hair samples.
  7. Please also send the completed order form together with the samples.

For a breeder or veterinarian discount please contact us before ordering.

Any information you include here is optional, but will be included on the certificate of results (except “Additional Info”).

Enter the name of your animal
Enter your animal's date/year of birth
Enter the breed name
Enter the registration number if known
Enter the microchip number
Is there anything else you would like to tell us about your horse? Reason for testing, symptoms etc.?

General Information

  • Foals may die shortly after birth due to organ failure (liver or heart).
  • Glucose cannot be stored as Glycogen → lack of nourishment in muscles and organs.
  • Affected foals usually die within the first 8 weeks.


  • Spontaneous abortions
  • Weakness
  • Low body temperature
  • Accelerated breathing
  • Tremors

Inheritance and Genotypes

→ GSDIV/GBED is an autosomal recessive hereditary disease, meaning that horses with only one copy of the genetic variant (N/gsdiv) are clinically normal carriers while horses with two copies of the genetic variant (gsdiv/gsdiv) are affected.

Genotype: The horse is: Effects:
N/N normal. The horse does not have any copies of the genetic variants causative for GSDIV/GBED and therefore cannot pass it on to any offspring.
N/gsdiv a carrier. The horse is clinically healthy. The genetic variant causative for GSDIV/GBED will be passed on to its offspring with a probability of 50%.
gsdiv/gsdiv affected. The horse is affected and will not live long enough to reproduce.


  • Carriers may be bred to normal animals (N/gsdiv x N/N) without any risk of producing affected offspring. The offspring should also be tested before breeding to determine if they are carriers or normal.
  • Breeding two carriers (N/gsdiv x N/gsdiv) is not recommended due to the possibility of 25% of the offspring being affected.


Ward TL, Valberg SJ, Adelson DL, Abbey CA, Binns MM, and Mickelson JR. (2004). Glycogen branching enzyme (GBE1) mutation causing equine glycogen storage disease IV. Mamm Genome 15, 570-577.

Further information is available at Online Mendelian Inheritance in Animals.

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