Hereditary equine regional dermal asthenia, more commonly known as HERDA, is often thought of as a skin disease that affects mainly Quarter Horses, primarily in the cutting horse industry. However, a group of researchers recently questioned whether the debilitating disorder could affect tissues other than the skin, specifically those with high Type 1 collagen levels, such as tendons and large blood vessels.

"The HERDA phenotype includes loose, fragile, hyperextensible skin that is easily injured and heals poorly," explained Jacquelyn Bowser, DVM, PhD, Dipl. ACVIM, an equine internist at Mississippi State University, who performed the research during her PhD training. "Seromas (tumorlike collections of serum), hematomas (blood pockets), and ulcerations are reported to occur primarily along the dorsum (back) and progressively intensify in occurrence and severity with age.

"HERDA is also overrepresented in elite cutting horses, where one-third of the top hundred cutting horses (from 1985-2006) were confirmed HERDA carriers," she continued. "Twenty-seven percent of the lifetime earnings from progeny of these top 100 cutting sires are derived from 12 HERDA carriers."

Currently, she noted, HERDA has a prevalence of more than 28% in the cutting horse discipline