They Are Lesion

There is increasing recognition of clinical variants of lupus erythematosus. However, the diagnosis for dogs with chronic erosive juxtamucosal lesions with histopathology consistent with cutaneous lupus erythematosus (CLE) is unclear. This retrospective study described 21 such cases of mucocutaneous lesions in dogs proposed to have mucocutaneous lupus erythematosus (MCLE).

All dogs had chronic lesions of >2 months duration predominating at mucosae or mucocutaneous junctions. The lesions were incompletely responsive to appropriate antibiotic and antiseptic treatment and had histopathology consistent with CLE. Lesions commonly developed in the genital/perigenital area and perianal area with a lower frequency of involvement on perioral, periocular, and nasal skin. Most dogs had involvement of 2 or more regions. The earliest clinical signs were usually mucocutaneous erosion/ulceration, dyschezia, and/or dysuria. Mucocutaneous lesions were typically symmetrical and consisted of well-demarcated areas of erosion and ulceration, erythema, hyperpigmentation, and crusting without concurrent signs of systemic disease. Histological lesions consisted of lymphocyte-rich interface dermatitis with evidence of basal keratinocyte damage; evidence of bacterial infection was common.

Dogs responded well to varying treatment protocols (eg, glucocorticoids, niacinamide, tetracycline/doxycycline). Complete remission was achieved in 16/17 dogs, although some remained on low drug doses long-term. Treatment with oral glucocorticoids often led to shorter treatment times; relapses were common during drug tapering. This disease, distinct from discoid lupus erythematosus, is believed to be a variant of chronic CLE.

The presence of mucocutaneous ulcerations in dogs is always a disturbing finding after common causes are ruled out. Three diseases mimic MCLE. Histopathology is needed to differentiate these diseases, but there are some clinical findings that are helpful. The first differential is mucocutaneous pyoderma. Clinically, this is differentiated by its tendency to affect the nose or perioral skin, its less erosive presentation, and its response to antibiotic therapy. The second is mucocutaneous pemphigoid, which looks similar to MCLE. Biopsy is needed for differentiation, but lesions more commonly affect the oral cavity; perimucosal erosions often affect the mucosa itself, and vesicles and scars are present. The third is erythema multiforme, typically seen in association with extensive macules, papules, or plaques with a central clearing (target lesions).— Karen A. Moriello, DVM, DACVD