More info from the dog rescue board I'm on...
"Marginal Auricular Dermatosis affects Dachshunds. The cause is unknown, but it may be associated with abnormal microcirculation in the pinnae. Early lesions consist of alopecia, crusts, and scales around the margins of the pinnae. In chronic cases, the whole pinna may become alopecic, and painful ulceration, fissuring and lichenification may occur around the margins."
"Several immune-mediated diseases including pemphigus foliaceus, pemphigus erythematosus, bullous pemphigoid, systemic lupus erythematosis, discoid lupus erythematosis, cold agglutinin disease, and drug eruptions cause pinnal alopecia, crusting and ulceration. Pinnal inflammation and pruritis are frequent in canine atopy and food hypersensitivity."
A raw food diet is recommended by many.