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→ Skin blistering and ulcerations due to improper connection between skin and underlying tissue.


  • Large ulcerating skin lesions (especially on legs and buccal mucous membranes)
  • Tooth abnormalities
  • Skin blistering
  • Hoof detachment

General Information:

  • Inproper cell-cell adhesion causes skin layers to detach and blister, especially on legs and gums.
  • Symptoms are present during or shortly after birth.
  • Lesions may cause inflammation and early death.
  • Affected foals are usually euthanized because of poor quality of life.
  • A different mutation causing similar symptoms is known in Draft Horses.

Inheritance: autosomal recessive

→ Animals with two copies of the variant (jeb2/jeb2) are affected. Animals with only one copy of the variant are clinically normal carriers (N/jeb2).

Possible Genotypes:

Genotype The horse is:
N/N normal. The horse has no copies of the genetic variant causative for JEB-2 and therefore cannot pass it on to its offspring.
N/jeb2 a carrier. The horse is clinically normal. The genetic variant will be passed on to its offspring with a probability of 50%.
jeb2/jeb2 affected. The horse will not live long enough to reproduce.



  • Carriers may be bred to normal animals (N/jeb2 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/jeb2 x N/jeb2) is not recommended due to the possibility of 25% of the offspring being affected.
  • Affected animals (jeb2/jeb2) should not be used for breeding.

Test information: This test detects the deletion in the LAMA3 gene.

Graves, K. T., Henney, P. J. and Ennis, R. B. (2009), Partial deletion of the LAMA3 gene is responsible for hereditary junctional epidermolysis bullosa in the American Saddlebred Horse. Animal Genetics, 40: 35–41. doi: 10.1111/j.1365-2052.2008.01795.x

Further information
is available at the Online Mendelian Inheritance in Animals website.

Breeds affected:

American Saddlebred

Test #: H106

Samples: Blood, Hair

Price: 35 € (net)

Time required: 7-10 days

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