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Junctional Epidermolysis Bullosa 2 (JEB2)


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

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Product Information

Affected breeds: American Saddlebred and related breeds
Test #: H106
Description: Junctional Epidermolysis Bullosa 2 Genetic Testing

This test detects the deletion in the LAMA3 gene.

Samples: Hair, Blood
Time: 10 – 14 days

General Information

  • Improper 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 infection and early death.
  • Affected foals are usually euthanized because of poor quality of life.
  • A different mutation causing similar symptoms (JEB1) is known in Draft Horses.


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

Inheritance and Genotypes

→ JEB2 is an autosomal recessive hereditary disease, meaning that horses with only one copy of the genetic variant (N/jeb2) are clinically normal carriers while horses with two copies of the genetic variant (jeb2/jeb2) are affected.

Genotype: The horse is: Effects:
N/N normal. The horse does not have any copies of the genetic variant causative for JEB2 and therefore cannot pass it on to any offspring.
N/jeb2 a carrier.
The horse is clinically normal. The genetic variant causative for JEB2 will be passed on to its offspring with a probability of 50%.
jeb2/jeb2 affected. The genetic variant causative for JEB2 will be passed on to all offspring. All offspring will be carriers (N/jeb2).


  • 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.


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
Online Mendelian Inheritance in Animals.

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