Junctional epidermolysis bullosa (JEB)
Photo credit: John Baird, Guelph
JEB is a fatal disorder that has been documented in Belgian foals, related breeds and more recently, American Saddlebreds. A recessive mutation (two copies of the mutation are necessary to produce disease) results in a dysfunctional structural protein that serves to anchor skin cells within the dermis. There is no known treatment. Foals are usually euthanized after diagnosis, due to the pain associated with the disease. Those that are not euthanized usually die of infection within 2 weeks. Skin lesions appear as irregular ulcerated areas over bony prominences that become more extensive with age. Ulceration of the coronary band is usually present and may proceed to sloughing of the hooves (see photo).
The JEB mutation may have been present in the Belgian breed as early as the beginning of the 20th century. Testing of 8 farms revealed a 36% incidence of carriers among Belgians. Testing of all breeding stock and avoiding interbreeding of carriers is strongly recommended. A genetic test for JEB is available at the Veterinary Genetics Laboratory at the University of California, Davis and the University of Kentucky-Gluck Equine Research Center.