Hereditary junctional epidermolysis bullosa, HJEB – American Saddlebred

 

Gene: LAMC3

Transmission: Autosomal recessive

For an autosomal recessive genetic disease an animal must have two copies of the mutation in question to be at risk of developing the disease.  Both parents of an affected animal must be carriers of at least one copy of the mutation.  Animals that have only one copy of the mutation are not at risk of developing the disease but are carrier animals that can pass the mutation on to future generations.

Mutation: Deletion, LAMA3 gene; del.6589bp, exons 24-27

Medical system: Dermal

Breed: American Saddlebred

Age of onset of symptoms: At birth

Hereditary junctional epidermolysis bullosa (HJEB) in Saddlebred horses is a genetic disease characterized by very fragile skin and by the presence of blisters in the skin and in the mouth. The mutation that causes the disease is found in the gene that codes for the glycoprotein laminin 5 protein; this protein has several roles in maintaining the integrity of the skin.  Clinical signs in affected animals appear soon after birth: there are blisters within the mouth that go on to rupture and the teeth and enamel are abnormally formed.  Skin lesions are mainly found on friction points and there can even be loss of hoofs. The affected animal may die after a few days due to secondary bacterial infections.  Animals that survive are often euthanized for humanitarian reasons.

 

References:

OMIA link: [1677-9796]

Graves KT, Henney PJ, Ennis RB. (2009) Partial deletion of the LAMA3 gene is responsible for hereditary junctional epidermolysis bullosa in the American Saddlebred Horse. Anim Genet. 40(1):35-41. [pubmed/19016681]

Spirito F, Charlesworth A, Linder K, et al. (2002) Animal models for skin blistering: absence of lamini5 causes hereditary junctional mechanobullous disease in the Belgian horse. Journal of Investigative Dermatology 119(3):684-691. [pubmed/12230513]