![]() Skin smears can confirm Malassezia yeast, and a skin biopsy confirms keratinization defects such as vitamin A-responsive dermatosis. Photo 3: Alopecia and hyperpigmentation of the ear pinna in a dog with light-responsive alopecia.Įar edge seborrhea due to Malassezia yeast or keratinization disorders can present in breeds such as Yorkshire Terriers and cocker spaniels, respectively. However, if the condition persists after the appropriate scabies treatment is completed, atopy should be considered. It is certainly appropriate to treat for scabies, as anytime scabies is suspected, treatment should be initiated. This is often mistaken for scabies since these dogs are pruritic and can have a positive pinnal/pedal reflex. Photo 2: Crusty, seborrheic ear edges in a patient with hypothyroidism.Ītopy in some breeds such as Boxers and Labrador retrievers can manifest with crusty, alopecic ear edges. Specific breeds affected include Doberman Pinschers, Labrador Retrieverss, Boxers and English Bulldogs. This disease is seen primarily in the Midwest and in northern climates during dark winters, resulting in a lack of natural sunlight exposure. The results of blood work are usually normal, and, in contrast to hypothyroidism, no other systemic clinical signs are usually present. Light-responsive alopecia (Photo 3) can also present with symmetrical ear edge alopecia, seborrhea and hyperpigmentation. ![]() A free thyroxine blood concentration test (free T4) by equilibrium dialysis will help confirm the diagnosis. With hypothyroidism (Photo 2), weight gain, exercise intolerance, hyperpigmentation, seborrhea and symmetrical hair loss may be present. The key to differentiating between the two is assessing whether any other clinical signs are present. Photo 1: Alopecia and crusting of the ear edge in a dog with scabies.Įndocrine diseases that can produce ear edge changes include hypothyroidism and light-responsive alopecia. Often a positive pinnal/pedal reflex is present, but this may also be true in atopic patients, particularly in Boxers and Labrador Retrievers. ![]() Always check ear edge scrapings if alopecia or crusting is present, especially if the dog is pruritic. One or both ears may be affected, and the patients are usually pruritic. If the ear edges are affected, alopecia is the initial skin change followed by crusting, but be aware that some owners may pick off the ear edge crusts. Differential diagnoses, depending on the presence of accompanying clinical signs, include hypothyroidism, light-responsive alopecia, atopy, seborrhea, ear edge vasculitis, frostbite, fly strike and pemphigus foliaceus.Ĭanine scabies (Photo 1) most commonly affect the ear edges, hocks, elbows and ventral abdomen. However, not all ear edge dermatitis is due to scabies. When pruritus is present, canine scabies is the most likely cause of ear edge crusting in dogs. Depending on the cause, pruritus may or may not be present. Ear edge dermatoses in dogs can consist of alopecia, seborrhea, crusting, ulceration and necrosis.
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