Ear Margin Seborrhea
This condition is common in Dachshunds, although other breeds with pendulous pinnae may be affected. Lesions usually affect the apex of the pinnae on both sides but can progress to involve the whole ear margin. The cause is unknown. Lesions appear as waxy, gray to yellow scales adherent to the base of hair shafts. Plugs of hair can be easily epilated, leaving behind a shiny surface to the skin. In severe cases, the ear margins are edematous and fissured. Histologic findings include severe hyperkeratosis and follicular keratosis with dilated follicles filled with keratin debris. Differential diagnoses include sarcoptic mange, pinnal alopecia, proliferative thrombovascular necrosis, dermatophytosis, and frostbite. Dermatophytosis, in particular, can cause a scaling pinnal dermatitis in dogs, cats, and horses, but the ear margin is not typically involved and other areas of the body are generally affected as well. Treatment includes antiseborrheic shampoos (eg, sulfur, salicylic acid, benzoyl peroxide), keratolytic products, dioctyl sodium sulfosuccinate (DSS), and systemic medications that may help normalize the abnormal keratinization process (eg, vitamin A and synthetic retinoids, essential fatty acids). Topical or oral glucocorticoids and pentoxifylline (10–15 mg/kg, bid-tid) may be beneficial when severe inflammation and fissures develop.