Nasal dermatoses of dogs may be caused by many diseases. Lesions may affect the bridge of the nose, the planum nasale, or both. In pyoderma, dermatophytosis, and demodicosis, the haired portions of the nose are affected. In systemic lupus erythematosus or pemphigus, the whole muzzle is often crusted (with occasional exudation of serum) or ulcerated. In systemic and discoid lupus, and occasionally in pemphigus and cutaneous lymphoma, the planum nasale is depigmented, erythematous, and eventually may ulcerate. The normal “cobblestone” appearance of the nasal planum is effaced.
Nasal dermatosis due to solar radiation probably is a rare disease and may often be a misdiagnosis for the lupus variants. In true nasal solar dermatitis, the nonpigmented areas of the planum nasale are affected first, and occasionally the bridge of the nose may become inflamed and sometimes ulcerated. The lesions are worse in the summer, although lupus and pemphigus may also show this seasonal variation.
Any of the above diseases may affect the periocular areas. (Also see Immunologic Diseases: Systemic Lupus Erythematosus (SLE) and see Immunologic Diseases: Autoimmune Skin Disorders.) The sudden onset of nasal swelling, erythema, and exudation is often eosinophilic furunculosis; this is thought to be caused by an arthropod sting or bite. The protozoal disease leishmaniasis may cause depigmentation of the nasal planum.
Treatment depends on etiology. Diagnostic tests should include skin scrapings, bacterial and fungal cultures, and biopsies for both histopathology and immunologic testing, although such testing is not used as often as formerly, due to the increase in veterinary dermatopathologists who may be able to make the diagnosis based on histopathology alone. If systemic lupus erythematosus is considered, blood for an antinuclear antibody test should be obtained.
If the diagnosis is nasal solar dermatitis, a topical corticosteroid lotion (betamethasone valerate, 0.1%) may help relieve inflammation. Exposure to sunlight must be severely curtailed. Topical sunscreens may be effective but need to be applied at least twice daily. Treatment for eosinophilic furunculosis is systemic corticosteroids, prednisone or prednisolone at 1 mg/kg, bid for 1 wk, after which the dosage should be gradually decreased.
Last full review/revision July 2011 by Stephen D. White, DVM, DACVD