Data on fifty horses with hereditary equine regional dermal asthenia (HERDA; "hyperelastosis cutis") were collected on clinical, histopathological, ultrastructural and immunohistological findings. All horses were Quarter horses or of Quarter horse ancestry. Pedigree evaluation strongly supported an autosomal recessive mode of inheritance. The most common lesions were seromas/haematomas, open wounds, sloughing skin, and loose, easily tented skin that did not return to its initial position. Definitive diagnosis could not be made via histopathology, although the presence of tightly grouped thin and shortened collagen fibres arranged in clusters in the deep dermis was suggestive of the disease. Trichrome, acid orcein-Giemsa and immunohistochemical stains for collagens I and III showed no consistent abnormalities compared to control horses; an increase in elastic fibres was not a consistent finding. Electron microscopy showed no abnormalities in the periodicity of the collagen bundles; neither orientation nor variation of cross-section diameter of the collagen fibrils differentiated control from affected horses. The diagnosis of HERDA relies on clinical presentation, but may be supported by suggestive (although not pathognomonic) histopathological lesions.

This review describes the role of pH in cutaneous structure and function. We first describe the molecules that contribute to the acidity or alkalinity of the skin. Next, differences in cutaneous pH among species, among individuals of the same species and within individuals are described. The potential functions of cutaneous pH in normal and diseased skin are analysed. For example, cutaneous pH has a role in the selection and maintenance of the normal cutaneous microbiota. In addition, cutaneous acidity may protect the skin against infection by microbes. Finally, there is evidence that a cutaneous pH gradient activates pH-dependent enzymes involved in the process of keratinization.

A total of 100 Pseudomonas aeruginosa (P. aeruginosa) isolates were collected over a 1.5-year period from cases of canine otitis. Sensitivities to enrofloxacin, marbofloxacin, and orbifloxacin were determined using minimum inhibitory concentration testing (MICT). Isolates were also tested for sensitivities to enrofloxacin and marbofloxacin using disk-diffusion susceptibility testing (DDST). Isolates were significantly more sensitive to marbofloxacin than to enrofloxacin (z = -4.57; P<0.05) or orbifloxacin (z = -5.02; P<0.05). Agreement was 87% between MICT and DDST for marbofloxacin, with approximately equal numbers of overestimation and underestimation errors. Agreement was 74% between MICT and DDST for enrofloxacin, but DDST tended to overestimate the number of enrofloxacin-susceptible strains. These results suggest that marbofloxacin is more effective against P. aeruginosa than either enrofloxacin or orbifloxacin and that relying on DDST may lead to ineffective enrofloxacin treatment.

An 11-year-old cat was evaluated because of dyspnea. Since 11 months of age, the cat had hyperextensibility of the skin consistent with cutaneous asthenia. Radiographic examination revealed a diaphragmatic hernia with intestinal loops in the thorax. Electron microscopic examination of skin specimens revealed collagen fibers of highly variable diameter, consistent with cutaneous asthenia. The diaphragmatic hernia was surgically repaired and healed well. Four weeks later, a left-sided perineal hernia was repaired surgically, and 4 months later, a right-sided perineal hernia was repaired surgically and colopexy and cystopexy were performed. All surgical procedures were successful and tissues healed well. Dermatosparaxis is a rare hereditary disorder that commonly results in cutaneous fragility and hyperextensibility in affected animals. The diagnosis depends on clinical findings and light and electron microscopic changes in affected tissues. Surgical repair can be performed successfully in an affected cat, and healing of incisions can occur without complications.