The prevalence of apoptotic keratinocytes in equine epidermis: a retrospective light-microscopic study of skin-biopsy specimens from 253 horses with normal skin or inflammatory dermatoses

Immune-mediated dermatoses

Pemphigus foliaceus is the most common autoimmune skin disease in horses and is associated with the production of autoantibodies directed against surface proteins of the keratinocyte. Pemphigus vulgaris is a rare autoimmune skin disease in horses. Systemic lupus erythematosus and cutaneous lupus erythematosus are recognized in horses and both are rare. Bullous pemphigoid is a rare autoimmune disease in horses caused by immunologic attack of the basement membrane zone by autoantibodies. Erythema muliforme is an immunologic reaction in the skin in which keratinocyte cell death is the prominent change seen on biopsy. Purpura hemorrhagica is thought analogous to nonthrombocytopenic purpura in humans.

Prevalence of apoptotic epidermal keratinocytes in eosinophilic dermatoses of the cat: a retrospective light-microscopic study of 145 skin-biopsy specimens

A retrospective light-microscopic study was performed on skin-biopsy specimens from 145 cats with eosinophilic inflammatory dermatoses in order to determine the prevalence of apoptotic epidermal keratinocytes (AKs), the prevalence of eosinophils in close proximity to AKs, and whether there was a difference in the prevalence of AKs or the prevalence of eosinophils in close proximity to AKs based on histopathological reaction pattern. Overall, 62/145 (43%) specimens had AKs. Of the cases in which AKs were seen, 18% had eosinophils in close proximity to the AKs. The specimens were divided into three groups based on histopathological reaction pattern: perivascular-to-interstitial, diffuse, and nodular. No difference in the prevalence of AKs was found among the three histological groups. Because the sample size containing eosinophils in close proximity to AKs was too small to compare the three histological patterns individually, nodular and non-nodular patterns were compared. No difference in the presence of eosinophils in close proximity to AKs was found in these two subsets. More AKs were present if eosinophils were in close proximity to the AKs (range 1-9 with eosinophils near compared to 0-7 without).

Frequency of apoptotic keratinocytes in the feline epidermis: a retrospective light-microscopic study of skin-biopsy specimens from 327 cats with normal skin or inflammatory dermatoses

A retrospective light-microscopic study was performed on 294 biopsy specimens of haired skin from cats with various feline inflammatory dermatoses and specimens from cats with normal skin. Conditions expected to frequently have apoptotic epidermal keratinocytes (AKs) (including erythema multiforme, systemic lupus erythematosus, thymoma-associated exfoliative dermatitis, solar dermatitis, and viral dermatopathies) were found to have significantly more AKs than other types of inflammatory dermatoses. Nevertheless, we found more than two AKs in many skin-biopsy specimens from inflammatory conditions not expected to have frequent AKs (especially those from ectoparasitic dermatoses). Only a single AK was found in 1/33 cats with normal skin.