Tensile properties in collagen-rich tissues of Quarter Horses with hereditary equine regional dermal asthenia (HERDA).
Authors: Bowser J E, Elder S H, Pasquali M, Grady J G, Rashmir-Raven A M, Wills R, Swiderski C E
Journal: Equine veterinary journal
Summary
# Editorial Summary: Tensile Properties in Collagen-Rich Tissues of Quarter Horses with HERDA Hereditary equine regional dermal asthenia (HERDA) is an autosomal recessive condition affecting Quarter Horses, caused by a missense mutation in the PPIB gene that encodes cyclophilin B—a protein critical for proper collagen folding and post-translational modification. Bowser and colleagues examined tissue samples from affected and unaffected horses to characterise how this genetic defect compromises the mechanical properties of collagen-dependent structures. The researchers found significantly reduced tensile strength and altered load-bearing capacity in skin and other collagen-rich tissues from HERDA-affected animals, reflecting impaired collagen fibril assembly and cross-linking. These findings explain the characteristic skin fragility and regional tissue breakdown seen clinically in affected horses, and underscore why HERDA horses are unsuitable for work and prone to life-threatening wounds from minor trauma. For equine professionals managing these animals, understanding that HERDA represents a fundamental structural defect—rather than a treatable inflammatory or nutritional problem—reinforces the importance of selective breeding against the mutation and humane management protocols for affected individuals.
Read the full abstract on PubMed
Practical Takeaways
- •HERDA is a genetic disorder with skin fragility as primary clinical sign; affected horses should not be bred as carriers will pass the recessive trait
- •Genetic testing of Quarter Horse breeding stock can identify carriers of the PPIB mutation to prevent affected offspring
- •Horses with HERDA require careful management to minimize skin trauma and complications from fragile integument
Key Findings
- •HERDA is an autosomal recessive disorder affecting Quarter Horses characterized by skin fragility
- •Affected horses carry a missense mutation in peptidyl-prolyl cis-trans isomerase B (PPIB) gene encoding cyclophilin B
- •The PPIB mutation impairs collagen folding and post-translational modifications in fibrillar collagen