FC‐12 Diagnostic value of skin biopsy in feline symmetric alopecia

Abstract

Feline symmetric alopecia (SA) is classified aetiologically as idiopathic or self‐induced, the latter due to allergic or psychogenic causes. It is characterized clinically by truncal alopecia not accompanied by skin lesions. Aetiology‐specific histopathological findings of SA have been reported. Idiopathic SA is characterised by follicular atrophy and telogenization, allergy‐induced alopecia by mild epidermal hyperplasia and superficial perivascular dermatitis (SPVD), and psychogenic‐induced alopecia by normal skin. The objective of this study was to assess the diagnostic value of histopathological examination to establish the aetiology of feline SA. Eighteen skin biopsies from cats with clinical histories suggestive of self‐induced SA were retrospectively evaluated. Nine control cats with normal hair and skin were included in the study. Sixty‐five per cent of 1230 and 72% of 1208 hair follicles evaluated in alopecic and control cats, respectively, were in the resting phase. Hairs and hair follicles with morphology resembling what is defined as trichomalacia in human trichotillomania were observed in two study cats. Mild epidermal hyperplasia was observed in two alopecic cats, and mild lymphocytic SPVD was present in 72% of alopecic and 66% of control cats, respectively. Results obtained in this study showed that high numbers of resting follicles are common in cats with normal hair and cats with self‐induced SA. Consequently, their presence cannot be considered a diagnostic criterion of idiopathic SA. In addition, because SPVD was common in normal feline skin, it might not be suggestive of allergy‐induced alopecia. Therefore, skin biopsy is not recommended to define the aetiology of feline SA. Funding: Self‐funded.