Diseases of the Pinna

Chapter 58 Diseases of the Pinna



The pinna is a mobile structure designed to localize and collect sound waves and transmit them to the tympanic membrane. The pinna has vastly different breed conformations in the dog, while in the cat; there is very little breed variation. The auricular cartilage expands to form the pinna, with the skin of the concave portion of the pinna tightly adherent to this cartilage. The cartilage of the pinna becomes funnel shaped at the opening of the external ear canal.


The pinna is a region of the body prone to numerous skin diseases. In most cases, the pinnal lesions are associated with lesions on other body areas. There are a few diseases where lesions are limited to the pinna (Table 58-1).


Table 58-1 DERMATOSES OF THE PINNA




































































































Affected Site(s) Disease Clinical Lesions Found on Pinna
Pinna only
  Canine eosinophilic pinnal folliculitis Erythema, papules, crusts
Ear margin seborrhea Scale, fissures
Fly bite dermatitis Ulcers, crusts, erythema, alopecia
Proliferative thrombovascular necrosis of the ear pinnae Ulcers, scale, hyperpigmentation
Pinna and other body areas
  Actinic keratoses Erythema, hyperkeratosis, crusts, hyperpigmented plaques
Arteriovenous fistula Edema
Atopic dermatitis Erythema
Canine demodicosis Erythema, papules, scale, alopecia, crusts
Canine sarcoptic mange Erythema, papules, crusts, scale, alopecia, excoriations
Contact dermatitis Erythema, macules, papules, erosions, ulcers
Cutaneous adverse food reaction Erythema
Dermatomyositis Alopecia, erythema, scale, crusts, ulcers, scars
Dermatophytosis Erythema, alopecia, papules, pustules, crusts
Discoid lupus erythematosus Alopecia, crusts, ulcers
Feline demodicosis Erythema, papules, scale, alopecia, crusts
Feline sarcoptic mange Erythema, papules, crusts, scale, alopecia, excoriations
Frostbite Ulcers, necrosis
Hereditary lupoid dermatosis of German short-haired pointers Scale, crusts
Juvenile cellulitis Papules, pustules, crusts
Malassezia pachydermatis Erythema, alopecia, scale, crusts, hyperpigmentation lichenification
Melanoderma and alopecia in Yorkshire terriers Alopecia, hyperpigmentation
Pattern baldness Alopecia, hyperpigmentation
Pemphigus erythematosus Erythema, scale, papules, pustules, alopecia, crusts
Pemphigus foliaceus Erythema, scale, papules, pustules, alopecia, crusts
Psoriasiform-lichenoid dermatosis of springer spaniels Erythema, hyperpigmentation, plaques, papules
Sebaceous adenitis Papules, alopecia, scale, follicular casts
Systemic lupus erythematosus Alopecia, crusts, ulcers
Vasculitis Erythema, alopecia, ulcers, crusts, necrosis
Zinc-responsive dermatosis Erythema, scale, crust, hyperkeratotic plaques

The work-up for all animals with pinnal disease should include a complete history, general physical examination, and dermatologic examination. Next, an otoscopic examination is performed, as well as microscopic examinations of skin scrapings for mites and fungi, cytology for bacteria and yeast, and mineral oil swabs for mites (Otodectes cynotis and Demodex spp.). A bacterial culture is indicated if rod bacteria are seen cytologically. Further testing may be needed such as a complete blood count, serum biochemical profile, urinalysis, allergy testing, food elimination trial, and skin biopsy for histopathology of the ear pinna (see Chapter 59 for diagnosis and treatment of otitis externa).




The biopsy technique of the ear pinna can be difficult. For lesions on the margin of the pinna, a wedge biopsy is preferred, while for central lesions, a small punch biopsy, size 3.5 to 4 mm, is used to obtain samples. For additional information on the skin biopsy technique, please refer to Chapter 37).



INFECTIOUS DISEASES



Dermatophytosis (also see Chapter 42)










Parasitic Diseases



Sarcoptic Mange (also see Chapter 44)







Feline Demodectic Mange (also see Chapter 43)




Aug 27, 2016 | Posted by in SMALL ANIMAL | Comments Off on Diseases of the Pinna
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