Hereditary equine regional dermal asthenia (“hyperelastosis cutis”) in 50 horses: clinical, histological, immunohistological and ultrastructural findings.

The study examines and reports on the clinical, histological, and ultrastructural findings in fifty Quarter horses diagnosed with hereditary equine regional dermal asthenia (HERDA), a skin condition. Based on the observed conditions and pedigree evaluation, the researchers suggest that HERDA is likely inherited as an autosomal recessive trait.

Research Methods and Findings

• The research was conducted on fifty horses that were either Quarter horses or possessed Quarter horse ancestry. These horses were all suffering from a condition known as hereditary equine regional dermal asthenia (HERDA), also known as “hyperelastosis cutis”. The findings were categorised into clinical, histopathological, ultrastructural, and immunohistological subsets.
• The scientists used pedigree evaluation to confirm suspected assumptions that HERDA is likely transmitted through an autosomal recessive mode of inheritance.
• The most common types of skin lesions found in the horses were seromas or haematomas, open wounds, sloughing skin, and skin that didn’t return to its normal position after being tented.
• Interestingly, histopathology alone couldn’t distinctly diagnose HERDA, although the presence of thin and shortened collagen fibres grouped tightly and organised in clusters within the deep dermis hinted towards the disease.
• A variety of staining methods were used to analyse the tissues, including trichrome, acid orcein-Giemsa, and the use of immunohistochemical stains for collagens I and III. These techniques showed no glaring deviations when compared to the tissues of healthy horses. Notably, an increase in elastic fibres was not found to be a consistent indicator of HERDA.
• Even with the help of electron microscopy to study the collagen bundles at a microscopic level, the researchers did not identify abnormal characteristics that significantly differentiated affected horses from their healthy counterparts.

Conclusion

• The study concludes that a diagnosis of HERDA primarily relies on the clinical presentation of symptoms instead of definitive histopathological lesions. However, histopathological findings may be used to guide the diagnosis process as they often exhibit suggestive abnormalities.