Hereditary equine regional dermal asthenia (HERDA), also known as hyperelastosis cutis (HC), is an inherited autosomal recessive connective tissue disorder.
[2] Symptoms typically don’t appear until the horse is subjected to pressure or injury on their back, neck or hips, usually around two years of age.
Research of affected animals indicated that 95% of the identified HERDA horses have traced back to Poco Bueno on both sides of the pedigree.
[5] Researchers at Mississippi State University described a separation of the upper and lower dermis associated with a loose packing of collagen fibrils in a one-year-old filly with hyperelastosis cutis.
[6] In 2004, clinical veterinarians at the University of California, Davis first coined the term hereditary equine regional dermal asthenia (HERDA) after examining 50 horses with stereotypical presentation of the disease.
[7] Shortened and thinned collagen fibrils in the deep dermis was the significant characteristic shared among the affected skin of diseased horses.
[9] In January 2007, UC Davis presented their findings at the Plant and Animal Genome Conference Equine Workshop indicating the ability to identify horses that carry HERDA.
[10] A full accounting of this work, detailing the mapping and identification of a mutation in the gene coding for peptidylprolyl isomerase B, was published on May 11, 2007.