Dermis may be fibrotic. Epidermis is hyperplastic. If the condition is acute, we would expect grossly detectable edema and hyperemia. If chronic, we may see nonspecific changes of a chronic hyperplastic dermatitis, such as thickened, hyperkeratotic, hyperpigmented skin. Since this pattern is so generic, we must be careful to evaluate concurrent changes present to help with the differential diagnosis.
Higher magnification reveals eosinophils are prominent.
In this case, type I hypersensitivity plays a major role in the pathogenesis in this case. Low Power Higher Power Gross Lesion example of a PV dermatitis provided is the clinical photo of a horse with chronic Culicoides insect bite hypersensitivity. This is chronic allergic dermatitis complicated by self trauma secondary to pruritus. Observations on Canine Atopy.