disease of ear pinna

A variety of dermatologic conditions affect the pinna. Most conditions cause lesions elsewhere as well. Rarely, a disease affects the pinna alone, or the pinna is the initial site affected. As with all dermatologic conditions, a diagnosis is best made with the results of a thorough history, a complete physical and dermatologic examination, and with careful selection and evaluation of specific diagnostic tests.
Insects and parasites commonly cause pinnal dermatitis either through direct damage from the bite of the parasite or as a result of hypersensitivity. Ticks can cause irritation at the site of attachment and may be found on the pinna or in the ear canal. The spinous ear tick ( Otobius megnini ), found in the southwestern USA, south and central Americas, southern Africa, and India, is a soft-shelled tick whose larval and nymphal forms parasitize the external ear canal of horses, cattle, sheep, goats, deer, rabbits, cats, and dogs. Clinical signs include head shaking, head rubbing, or drooped pinnae. Both the animal and the environment should be treated. Pyrethrin/pyrethroid products are effective.
Fly strike is a worldwide problem caused by the stable fly, Stomoxys calcitrans , and typically affects dogs and horses. The fly bite causes small papules and wheals with central hemorrhagic crusts that itch. Lesions are found on the tips or on the folded surface of the pinnae of dogs with flopped ears. However, in horses this fly can cause a hypersensitivity reaction or severe dermatitis resulting in lesions on the dorsal and/or ventral trunk and face in addition to the pinna. Treatment includes fly repellents, controlling the fly population with environmental clean up (manure, etc), and insecticides.
Equine aural plaques ( papillary acanthoma, ear papillomas) are caused by a papillomavirus. Black flies ( Simulium spp ) are likely the mechanical vector. These flies are active at dawn and dusk, when they attack the head, ears, and ventral abdomen of horses. Clinically, the lesions are characterized by depigmented, hyperkeratotic, coalescing papules and plaques localized to the concave aspect of the pinna. Often both pinnae are affected. Similar lesions may be present around the anus and external genitalia. Lesions are usually asymptomatic, but in some cases the direct effect of the fly bite causes dermatitis and discomfort. Histologically, the lesions are characterized by mildy papillated epidermal hyperplasia and marked hyperkeratosis. Increased size of keratohyalin granules, poikilocytosis, and hypomelanosis may also be present in the epidermis. Intranuclear viral particles have been seen in electron microscopic studies. Treatment includes frequent applications of fly repellent and stabling the horse during the fly’s feeding times. Lesions typically do not regress.
An allergic reaction to mosquito bites can cause an ulcerative and crusted dermatitis of the pinnae, nose, and rarely the footpads and eyelids of cats. Lesions progress from papules to plaques to crusted ulcers that coalesce to affect extensive areas. Pruritus is variable and lymphadenopathy may occur. Histologically, the lesions are characterized by severe superficial and deep perivascular to interstitial eosinophilic dermatitis, often associated with folliculitis and furunculosis. The differential diagnoses include pemphigus foliaceus, other causes of eosinophilic dermatitis (food allergy, atopy, idiopathic), Notoedres cati , and dermatophytosis. Treatment includes keeping the animal inside and using a pyrethrin repellent when exposure to mosquitos is anticipated. Systemic glucocorticoids may be necessary in severe cases.
Sarcoptiform mite infestation ( Sarcoptes scabiei , Notoedres cati ) is common in pigs, dogs, and cats throughout the world. In the USA, sarcoptic mange is rare in horses, cattle, and sheep and is considered a reportable disease. Papular eruptions progress to scaling, crusting, and excoriations of the ear margins and other parts of the body. Pruritus is severe. Transmission is by direct contact with infected animals. Diagnosis is based on clinical signs, history of exposure, and discovery of mites on multiple skin scrapings. Negative scrapings do not rule out the diagnosis, however, as the mite is often difficult to find. If the diagnosis is suspected, treatment should be instituted. Treatment options include lime sulfur dips (safe in all species) every 5 days for 3-5 treatments, insecticidal dips such as amitraz (in dogs only) 2-3 treatments 2 wk apart, and ivermectin at 200-300 mg/kg, PO or SC, every 1-2 wk for 2-4 treatments. Ivermectin is widely used to treat sarcoptic mange in dogs, and has been used to treat notoedric mange in cats, but is not approved by the FDA for this indication. Therefore, every caution should be taken and clients specifically informed of inherent risks with this drug. It should not be used in Collies, Shetland Sheepdogs, Australian Shepherds, and Old English Sheepdogs. Oral milbemycin oxime has been reported to be effective in the treatment of canine sarcoptic mange but is not FDA approved for this purpose. The recommended treatment protocol is 2 mg/kg once weekly for 4 treatments. Because mites can survive off the host for a variable amount of time, all bedding, brushes, tack, and fomites should be treated as well.
Nonburrowing psoroptic mites cause a pruritic otitis externa in horses. Horses may present with head shaking and a drooping ear. Diagnosis is confirmed by finding the mites on skin scraping or in otic exudate, but mites may be difficult to find in the ear canal. Psoroptic mange is a reportable disease in some regions. Ivermectin at 200 mg/kg, PO, every 2 wk for 2 treatments has been shown to be effective.
Several ear margin dermatoses characterized by alopecia have been described in dogs. Periodic pinnal alopecia in Miniature Poodles is characterized by progressive bilateral alopecia of the convex surfaces of the ear. The hair loss is acute in onset and progresses over several months, but hair may spontaneously regrow. There are no other clinical signs. Treatment is unnecessary.
Pinnal alopecia has been reported in Dachshunds, Chihuahuas, Italian Greyhounds, and Whippets and is thought to have a hereditary predisposition. The age of onset is ≤1 yr of age. Lesions start as thinning of the hair coat, and complete pinnal alopecia may occur by 8-9 yr of age. Other commonly affected areas are the ventral neck and thorax and the caudal medial thighs. The hair loss is asymptomatic. Differential diagnoses for this condition are endocrinopathies (eg, hypothyroidism, hyperadrenocorticism, ****** hormone imbalance). Histologically, the skin is normal and hair follicles are diminished in size but normal in appearance. No effective treatment has been reported, but pentoxifylline (10 mg/kg, bid-tid ), melatonin (3 mg for small breeds and 6 mg for large breeds, bid-tid ), and topical minoxidil have anecdotally been described as helpful.
Ear margin seborrhea or ear margin dermatosis 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 scale 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 (vitamin A and synthetic retinoids; essential fatty acids). Topical or oral glucocorticoids and pentoxifylline (10 mg/kg, bid-tid ) may be beneficial when severe inflammation and fissures develop.
Several immune-mediated diseases such as pemphigus foliaceus, pemphigus erythematosus, drug eruption, toxic epidermal necrolysis, and immune vasculitis may affect the pinna and the ear canal. ( See also autoimmune skin disorders , Autoimmune Skin Disorders.) Other areas of the body are typically affected and may include footpads, mucous membranes, mucocutaneous junctions, nails and nail beds, and the tip of the tail. Immune-mediated diseases are confirmed with biopsy of primary lesions (papules, vesicles, pustules, erythematous margins of secondary lesions) with histologic evaluation by a dermatopathologist.
Acquired folded ear tips in cats are most often associated with longterm glucocorticoid therapy (eg, daily eye or otic preparations). It may also be caused by solar radiation damage. Ear folding may not be reversible.
Feline solar dermatitis or actinic dermatitis is seen most commonly in white cats or cats with white pinnae that have been chronically exposed to sun. Lesions first appear as erythema and scaling on the sparsely-haired tips of the ears. Crusting, exudation, and ulceration may develop as the actinic keratosis undergoes transformation into a squamous cell carcinoma. During early stages of the disease, treatment consists of limiting exposure to ultraviolet light through confinement indoors between the hours of 10 am and 4 pm, and the use of topical sunscreens. Squamous cell carcinoma of the pinnae is treated with surgical excision followed by radiation therapy.
Auricular hematomas are small to large fluid-filled swellings that develop on the concave surface of the pinnae in dogs, cats, and pigs. The pathogenesis for the development of the lesions is unknown, but head shaking or ear scratching due to pruritus is always involved. In dogs, the condition is seen with atopy and food allergy in which the ear canals are the primary sites of allergic inflammation and pruritus. In pigs, sarcoptic mange, pediculosis, and meal in the ears (from overhead feeders) have been implicated as a cause of head-shaking that has led to auricular hematomas. Bites from other pigs also may be at fault (see necrotic ear syndrome, Necrotic Ear Syndrome in Swine). Treatment is surgical to allow drainage. After draining and flushing, several mattress sutures can be placed to eliminate the pocket. The addition of a drain made out of a teat tube, piece of soft urinary catheter, or IV catheter increases the success rate of the surgery. Drainage and glucocorticoid instillation are successful in ~50% of cases. Drainage is best obtained with a butterfly connection or an IV catheter. Glucocorticoids are instilled to fill the cavity without causing skin distention. A short course of a low anti-inflammatory dose of oral glucocorticoids is commonly added to this treatment.
Proliferative vascular necrosis of the pinnae is rare in dogs. There are no known breed, ******, or age predilections and the etiology is also unknown. Lesions, which consist of scaly, thickened, hyperpigmented skin surrounding a necrotic ulcer, begin at the apex of the ear and spread along the concave surface. Eventually, necrosis may deform the margin of the pinna.
Auricular chondritis has been reported rarely in cats and in 1 dog. Clinical signs include pain, swelling, erythema, and deformation of the pinnae. Both ears are typically affected. Lesions consist of lymphoplasmacytic infiltrates, basophilia, and necrosis of cartilage. Treatment may not be required if the condition is nonpainful. Systemic glucocorticoids have been reported to be ineffective, but dapsone (1 mg/kg, sid ) has induced remission in some cases.
Frostbite may occur in animals poorly adapted to cold climates and is more likely in wet or windy conditions. It typically affects body regions that are poorly insulated, including the tips of the ears. The skin may be pale or erythematous, edematous, and painful. In severe cases, necrosis and sloughing of the tips may follow. Treatment consists of rapid, gentle warming and supportive care. Amputation of affected regions may be required but should be delayed until the extent of viable tissue is determined.
Canine juvenile cellulitis is an uncommon disorder of puppies and is characterized by granulomatous, sterile pustules of the face, pinnae, and submandibular lymph nodes. It occurs in puppies 3 wk to 4 mo of age and rarely in older animals. Golden Retrievers, Gordon Setters, and Dachschunds appear to be at greater risk than other breeds. A pustular otitis externa is common, along with edematous, thickened pinnae. The diagnosis can be confirmed by biopsy, which shows a pyogranulomatous inflammatory infiltrate with no microorganisms, and by negative bacteriologic culture. Early treatment is recommended to avoid scarring. Prednisone or prednisolone (2 mg/kg, PO, divided bid) should be tapered slowly over 4-6 wk or until the disease is inactive. Antibiotics may be needed to treat secondary bacterial infection
Equine aural plaques ( papillary acanthoma, ear papillomas) are caused by a papillomavirus. Black flies ( Simulium spp ) are likely the mechanical vector. These flies are active at dawn and dusk, when they attack the head, ears, and ventral abdomen of horses. Clinically, the lesions are characterized by depigmented, hyperkeratotic, coalescing papules and plaques localized to the concave aspect of the pinna. Often both pinnae are affected. Similar lesions may be present around the anus and external genitalia. Lesions are usually asymptomatic, but in some cases the direct effect of the fly bite causes dermatitis and discomfort. Histologically, the lesions are characterized by mildy papillated epidermal hyperplasia and marked hyperkeratosis. Increased size of keratohyalin granules, poikilocytosis, and hypomelanosis may also be present in the epidermis. Intranuclear viral particles have been seen in electron microscopic studies. Treatment includes frequent applications of fly repellent and stabling the horse during the fly’s feeding times. Lesions typically do not regress.
An allergic reaction to mosquito bites can cause an ulcerative and crusted dermatitis of the pinnae, nose, and rarely the footpads and eyelids of cats. Lesions progress from papules to plaques to crusted ulcers that coalesce to affect extensive areas. Pruritus is variable and lymphadenopathy may occur. Histologically, the lesions are characterized by severe superficial and deep perivascular to interstitial eosinophilic dermatitis, often associated with folliculitis and furunculosis. The differential diagnoses include pemphigus foliaceus, other causes of eosinophilic dermatitis (food allergy, atopy, idiopathic), Notoedres cati , and dermatophytosis. Treatment includes keeping the animal inside and using a pyrethrin repellent when exposure to mosquitos is anticipated. Systemic glucocorticoids may be necessary in severe cases.
Sarcoptiform mite infestation ( Sarcoptes scabiei , Notoedres cati ) is common in pigs, dogs, and cats throughout the world. In the USA, sarcoptic mange is rare in horses, cattle, and sheep and is considered a reportable disease. Papular eruptions progress to scaling, crusting, and excoriations of the ear margins and other parts of the body. Pruritus is severe. Transmission is by direct contact with infected animals. Diagnosis is based on clinical signs, history of exposure, and discovery of mites on multiple skin scrapings. Negative scrapings do not rule out the diagnosis, however, as the mite is often difficult to find. If the diagnosis is suspected, treatment should be instituted. Treatment options include lime sulfur dips (safe in all species) every 5 days for 3-5 treatments, insecticidal dips such as amitraz (in dogs only) 2-3 treatments 2 wk apart, and ivermectin at 200-300 mg/kg, PO or SC, every 1-2 wk for 2-4 treatments. Ivermectin is widely used to treat sarcoptic mange in dogs, and has been used to treat notoedric mange in cats, but is not approved by the FDA for this indication. Therefore, every caution should be taken and clients specifically informed of inherent risks with this drug. It should not be used in Collies, Shetland Sheepdogs, Australian Shepherds, and Old English Sheepdogs. Oral milbemycin oxime has been reported to be effective in the treatment of canine sarcoptic mange but is not FDA approved for this purpose. The recommended treatment protocol is 2 mg/kg once weekly for 4 treatments. Because mites can survive off the host for a variable amount of time, all bedding, brushes, tack, and fomites should be treated as well.
Nonburrowing psoroptic mites cause a pruritic otitis externa in horses. Horses may present with head shaking and a drooping ear. Diagnosis is confirmed by finding the mites on skin scraping or in otic exudate, but mites may be difficult to find in the ear canal. Psoroptic mange is a reportable disease in some regions. Ivermectin at 200 mg/kg, PO, every 2 wk for 2 treatments has been shown to be effective.
Several ear margin dermatoses characterized by alopecia have been described in dogs. Periodic pinnal alopecia in Miniature Poodles is characterized by progressive bilateral alopecia of the convex surfaces of the ear. The hair loss is acute in onset and progresses over several months, but hair may spontaneously regrow. There are no other clinical signs. Treatment is unnecessary.
Pinnal alopecia has been reported in Dachshunds, Chihuahuas, Italian Greyhounds, and Whippets and is thought to have a hereditary predisposition. The age of onset is ≤1 yr of age. Lesions start as thinning of the hair coat, and complete pinnal alopecia may occur by 8-9 yr of age. Other commonly affected areas are the ventral neck and thorax and the caudal medial thighs. The hair loss is asymptomatic. Differential diagnoses for this condition are endocrinopathies (eg, hypothyroidism, hyperadrenocorticism, ****** hormone imbalance). Histologically, the skin is normal and hair follicles are diminished in size but normal in appearance. No effective treatment has been reported, but pentoxifylline (10 mg/kg, bid-tid ), melatonin (3 mg for small breeds and 6 mg for large breeds, bid-tid ), and topical minoxidil have anecdotally been described as helpful.
Ear margin seborrhea or ear margin dermatosis 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 scale 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 (vitamin A and synthetic retinoids; essential fatty acids). Topical or oral glucocorticoids and pentoxifylline (10 mg/kg, bid-tid ) may be beneficial when severe inflammation and fissures develop.
Proliferative vascular necrosis of the pinnae is rare in dogs. There are no known breed, ******, or age predilections and the etiology is also unknown. Lesions, which consist of scaly, thickened, hyperpigmented skin surrounding a necrotic ulcer, begin at the apex of the ear and spread along the concave surface. Eventually, necrosis may deform the margin of the pinna.
Auricular chondritis has been reported rarely in cats and in 1 dog. Clinical signs include pain, swelling, erythema, and deformation of the pinnae. Both ears are typically affected. Lesions consist of lymphoplasmacytic infiltrates, basophilia, and necrosis of cartilage. Treatment may not be required if the condition is nonpainful. Systemic glucocorticoids have been reported to be ineffective, but dapsone (1 mg/kg, sid ) has induced remission in some cases.
Frostbite may occur in animals poorly adapted to cold climates and is more likely in wet or windy conditions. It typically affects body regions that are poorly insulated, including the tips of the ears. The skin may be pale or erythematous, edematous, and painful. In severe cases, necrosis and sloughing of the tips may follow. Treatment consists of rapid, gentle warming and supportive care. Amputation of affected regions may be required but should be delayed until the extent of viable tissue is determined.
Canine juvenile cellulitis is an uncommon disorder of puppies and is characterized by granulomatous, sterile pustules of the face, pinnae, and submandibular lymph nodes. It occurs in puppies 3 wk to 4 mo of age and rarely in older animals. Golden Retrievers, Gordon Setters, and Dachschunds appear to be at greater risk than other breeds. A pustular otitis externa is common, along with edematous, thickened pinnae. The diagnosis can be confirmed by biopsy, which shows a pyogranulomatous inflammatory infiltrate with no microorganisms, and by negative bacteriologic culture. Early treatment is recommended to avoid scarring. Prednisone or prednisolone (2 mg/kg, PO, divided bid) should be tapered slowly over 4-6 wk or until the disease is inactive. Antibiotics may be needed to treat secondary bacterial infection.