CANINE & FELINE AUTOIMMUNE & IMMUNE MEDIATED DISEASES: DERMATOLOGY AN UPDATE PART 2 Rod A.W. Rosychuk DVM, DACVIM Selected Lupus and Lupus-like Diseases Discoid Lupus Erythematosus (DLE)

DLE in dogs is seen primarily in younger dogs (2–4 years of age) as a depigmenting and inflammatory disease of the nasal planum, bridge of the nose, periocular region, mucocutaneous areas of the lips, and occasionally the pinna. A variant of the disease (or perhaps a different disease?) is seen primarily in Australian shepherds and “white” dolicocephalic dogs, resulting in very severe atrophy and erosion of the planum. DLE usually sun sensitizes the skin. The histology of DLE classically involves variable epidermal atrophy and hyperplasia, hydropic degeneration, and single cell necrosis within the basal cell layer and a superficial dermal accumulation of lymphocytes, lymphocytes and plasma cells, or predominantly plasma cells. The infiltrate may be band-like (lichenoid reaction) and may obscure the dermoepidermal junction. There is usually pigmentary incontinence and variable thickening of the basement membrane. Interestingly, in the author’s experience, only about half of the patients with clinical signs consistent with the disease have classic histopathology. The other half has a superficial dermal mononuclear dermatitis, but lacks the other changes of DLE. This may represent a DLE-like disease whose clinical presentation and response to medication mimics DLE. It has also been recently shown that the histopathology of mucocutaneous pyoderma affecting the planum (more common in German shepherds) may also overlap with that of DLE. Therapy for DLE has included sun restriction, sunscreens, topical glucocorticoid (e.g., betamethasone ointment, fluocinolone/DMSO [Synotic]), oral vitamin E (400–800 IU BID), omega 6/omega 3 fatty acids, topical 0.1% Tacrolimus (BID administration producing response in 65–75% of cases), oral tetracycline or doxycycline and niacinamide (producing 50–60% responses), oral prednisone /prednisolone, prednisolone and azathioprine, or gold salts. DLE is only rarely encountered in cats.