An inherited skin disease in Quarter horses, Appaloosas and Paints is called HERDA, the acronym for heritable equine regional dermal asthenia. HERDA is one of the most commonly reported inherited diseases in horses. Affected horses have hyperextensible skin, meaning it stretches more than normal equine skin. The horses get skin lesions and in many cases the skin sloughs off or dies, leaving an open wound, and then the area heals with a scar. In the Quarter horse industry, cutting horses are the most common to be affected as three of the 10 lifetime leading cutting horses sires are confirmed carriers of the disease.

Usually signs of the disease are not noticed until the horse is over a year of age, as some horses can have mild lesions and the problems are not seen until the horse enters training. In fact, some horses do not develop lesions until a saddle is used and skin lesions develop under the saddle. Unfortunately, there is no treatment for the disease. Lesions commonly develop over the dorsal back even without a saddle due to increased heat and ultraviolet light in this area. Although the major lesions of horses with HERDA are skin lesions, Dr. Ann Rashmir-Raven indicates in Vet Equine Clinics that other organ systems can also be affected including the eyes, musculoskeletal system and immune function. Mildly affected horses can be ridden and some have even lived into their 20s by minimizing exposure to intense sunlight and heat, treating wounds early, and providing good nutrition. However, due to the seriousness of the disease, most horses are euthanized soon after the diagnosis. Hopefully, you will not have to deal with HERDA in your horses.