Atypical felid alphaherpesvirus 1 dermatitis in a cat

Feline herpesviral ulcerative dermatitis is associated with ulceration of the face and oral mucosa. Histologically, lesions consist of eosinophilic inflammation in the superficial dermis, with occasional eosinophilic intranuclear viral inclusion bodies in the epidermis, follicular epithelium, and associated glands. We describe a case of atypical felid alphaherpesvirus 1 (FeAHV1; family <i>Orthoherpesviridae</i>, taxon species <i>Varicellovirus felidalpha1</i>) dermatitis in a 6-y-old, castrated male, domestic shorthair cat in which lesions were located on the limbs and shoulder without facial or oral involvement. Histologic findings consisted of deep eosinophilic and plasmacytic dermatitis with vasculitis, thrombosis, and intranuclear viral inclusion bodies within macrophages. Immunohistochemistry (IHC) for FeAHV1 revealed viral antigen within macrophages in the deep dermis but not in epithelial cells. FeAHV1 was identified in the affected tissue via a consensus PCR assay targeting the DNA polymerase and the DNA packaging terminase subunit 1 for herpesviruses, followed by sequencing of the PCR amplicons. Similar lesions appeared on the right shoulder and right tarsal area ~7 mo after the first biopsy. Histologically, lesions were typical of feline ulcerative dermatitis and consisted of extensive areas of epidermal and follicular necrosis with ulceration and occasional intranuclear eosinophilic viral inclusion bodies in the epidermis and sebocytes. IHC in the second biopsy sample revealed FeAHV1 antigen within epithelial cells and macrophages near the ulcerated areas. Clinicians and pathologists should be aware of unusual manifestations of FeAHV1-associated ulcerative dermatitis in cats.