Hereditary equine regional dermal asthenia in three related Quarter horses in Brazil

Abstract

Hereditary equine regional dermal asthenia belongs to a group of inherited, congenital connective tissue dysplasias usually described as hyperelastosis cutis, cutaneous asthenia, dermatosparaxis, or Ehlers-Danlos-like syndrome. This report presents the clinical and histological features of three related Quarter horses affected with regional dermal asthenia. These horses had bilateral asymmetric lesions of the trunk and lumbar regions, where the skin was hyperextensible. Handling of the skin elicited a painful response and superficial trauma led to skin wounds. The skin was thinner than normal in the affected areas, with thickened borders and harder fibrotic masses (pseudotumours). The histopathological findings included thinner and smaller collagen fibrils, and a loose arrangement of collagen fibres in the middle, adventitial and deep dermis. Masson's trichrome and Calleja stains did not reveal any abnormality of collagen and elastic fibres. Electron microscopy showed no abnormalities. As in human patients, pseudotumour histopathological findings included fibroplasia and neovascularization. The pedigree chart of these animals supports an autosomal recessive type of inheritance, which has been suggested by other studies. This is the first report of this disease in Brazil. Its clinical and histological features resemble those described in horses affected with this condition in the United States.

Clinical and pathological findings in a HERDA‐affected foal for 1.5 years of life

“…The study also substantiates that horses with HERDA, even with frequent dermatological evaluations, may appear healthy for at least the first 1.5 years of life before showing severe clinical signs. As the disease has now been noted in South America 9 and Europe (B. Litschauer, personal communication, 2006) in addition to North America, it is increasingly important for the veterinary community to recognize the disease clinically and the limitations of a diagnosis via histopathology, particularly with regard to specimens from grossly normal skin.…”

Dermatological and morphological findings in quarter horses with hereditary equine regional dermal asthenia

“…First described as hyperelastosis cutis, hereditary equine regional dermal asthenia (HERDA) is an autosomal recessive disorder that is frequently observed in quarter horses (QHs) and their lineages . Hereditary equine regional dermal asthenia is clinically characterized by loose, hyperextensible and abnormally fragile skin, which is easily torn upon minor trauma, with seromas, haematomas, ulcers, scarring and tumour‐like masses developing primarily along the dorsum . A painful response may occur when the skin is manipulated …”

“…Thorough knowledge of the dermatological and morphological findings of HERDA‐affected horses and obtaining a definitive diagnosis are very important to minimize animal suffering and economic losses. However, only a few studies have reported the dermatological, morphological and molecular findings in QHs affected by HERDA worldwide . One study described the dermatological, morphological and ultrastructural findings in 50 HERDA‐affected horses and attempted to evaluate the accuracy of histopathological diagnosis.…”

Equine clinical genomics: A clinician's primer

“…Heterozygotes are not known to experience deleterious effects of the allele (Tryon et al 2009; Tryon et al 2007; Tryon et al 2005). HERDA has also been reported in Quarter Horses in Brazil (Borges et al 2005). …”