Proliferative and necrotizing otitis externa in four cats

Abstract

Proliferative and necrotizing feline otitis externa is a rare disorder of unknown aetiology. This condition was diagnosed by skin biopsy in three adult domestic shorthair cats (3-5 years old) and one kitten (6 months old). The affected cats had large tan to dark brown-black coalescing plaques covering the concave surface of the pinnae and external ear canals. Friable material from the plaques and a thick exudate occluded the ear canals. The cats had a secondary bacterial and/or yeast otitis. Prior to the histopathological diagnosis, all cats received numerous otic preparations as well as oral antibiotics and corticosteroids without resolution. Histologically, all cases had strikingly similar changes; acanthosis with pronounced hair follicle outer root sheath hyperplasia and neutrophilic luminal folliculitis, follicular keratosis and individually necrotic keratinocytes in the outer root sheath of hair follicles. One case was documented via skin biopsy to have persisted for 4 years. The adult cats were treated with topical 0.1% tacrolimus and all showed marked improvement although one cat was lost to follow up. The lesions completely resolved with topical tacrolimus alone in one cat and topical tacrolimus in addition to oral prednisolone in another cat.

Proliferative and necrotising otitis externa in a cat without pinnal involvement: video-otoscopic features

“…1 In this case, the age of onset is not defined clearly, as the affected cat was adopted at approximately 1 year of age and already showed bilateral ear pruritus.…”

Proliferative and necrotizing otitis externa in a kitten: successful treatment with intralesional and topical corticosteroid therapy

“…Although a few reports about PNOE have been published [1, 4, 9], the reported therapeutic options seem to be limited. Tacrolimus (FK506), is an immunosuppressive agent with a similar mechanism of action to cyclosporine, the most commonly used for PNOE [1, 4, 9]. On the other hand, glucocorticoid therapy has been reported to be ineffective or only partially effective [4].…”

“…Tacrolimus (FK506), is an immunosuppressive agent with a similar mechanism of action to cyclosporine, the most commonly used for PNOE [1, 4, 9]. On the other hand, glucocorticoid therapy has been reported to be ineffective or only partially effective [4]. Here, we describe the first juvenile case of PNOE in Japan, which was treated with local corticosteroid therapy alone.…”

“…PNOE is a rare disease that has only been mentioned in four reports [1, 2, 4, 9]. The pathogenesis of PNOE is currently being explored.…”

“…Epidermal and follicular hyperplastic changes are also observed in the feline dermatitis associated with viral infections. However, polymerase chain reaction analysis [2] and immunohistochemical staining [4] have ruled out infection by herpesvirus, calicivirus or papillomavirus. Instead, Videmont et al .…”