What Is Ear Margin Dermatosis?
Ear margin dermatosis is a common seborrheic disorder that affects the edges of the ears of several breeds, especially the dachshunds. The disorder usually begins in young adults and is characterized by replacement of normal epithelial cells by horny tissue. In severe untreated cases, a progression to ulceration and necrosis may be seen due to thrombosis of the capillaries supplying blood to the ear margins, which may result in severe scarring. Itchiness is usually absent, but alopecia may develop with time.
The diagnosis of ear margin dermatosis is based on the history, breed, and presence of the characteristic ear margin skin damage. Skin scrapings are performed to rule out scabies and demodicosis if severe itchiness is present. Diagnostic procedures to differentiate these diseases may require blood tests, blood chemistry profile, antinuclear antibody (ANA) testing, Coomb’s test, and biopsies. Coomb’s test is a test to detect non-agglutinating antibodies against red blood cells by use of anti-antibodies (the Coombs’ reagent.) The direct test is applied to freshly drawn blood to detect antibody bound to circulating red cells. The indirect test is applied to serum to detect the presence of antibodies that can bind to red blood cells.
Advanced lesions lead to head shaking and the development of fissures while the mild scaling form of ear margin dermatosis is usually controllable with topical therapy but rarely is curable. In the early marginal lesions, topical treatment with antiseborrheic agents (benzoyl peroxide, tar, sulfur, salicylic acid) will remove the greasy scales. In severe cases, topical glucocorticoid creams and systemic prednisone may be prescribed to reduce inflammation. Although the advanced ulcerative and necrotic stage is resistant to medical therapy, it can be cured by surgical removal of the affected ear margin and laser surgery.
- Karen Moriello – Small Animal Dermatology: Self-Assessment Color Review
- K. V.F. Jubb – Pathology of Domestic Animals