Idiopathic periadnexal multinodular granulomatous dermatitis in twenty-two dogs.

A distinctive periadnexal multinodular granulomatous dermatitis of unknown cause was diagnosed over a 6-year period in 22 dogs (13 males and nine females) aged 8 months to 10 years, purebred as well as mixed-breed. Nodules, usually more than two, started on the face and were often unaccompanied by signs of irritation. All dogs were otherwise healthy except a Viszla with bilateral anterior uveitis and a Basset hound with nasal congestion and sneezing. Microscopically, cutaneous lesions occurred in a periadnexal pattern, replaced sebaceous glands, coalesced, and extended into the subcutis and in more advanced cases through the panniculus carnosus. Infectious agents were not demonstrated by aerobic, anaerobic, or fungus cultures or by light or electron microscopy, nor were ectoparasites seen. Immunofluorescence and peroxidase-antiperoxidase techniques gave negative results for intraepidermal and basement membrane deposits of IgA, IgG, IgM, and C3. Lesions were unresponsive to a variety of antibiotics; they regressed spontaneously in two untreated dogs and rapidly in dogs given only corticosteroid therapy. Continuous low-dose corticosteroids were necessary in a few dogs to prevent recurrence.