• Cause: unknown (possibly immune-mediated etiology).
• Signs: young cats, <1 year of age; although reported in older cats. Lesions are bilaterally symmetrical in most cases. Affected cats have large tan to dark brown-black coalescing plaques over the concave aspect of the pinnae and extending into the vertical ear canals. The plaques are friable when handled and often there is a thick exudate in the external ear canal. Erosion and ulceration are common as the lesions progress. Secondary bacterial and/or yeast infection is common. The lesions can cause head shaking, marked pruritus, pain, depression and anorexia. Therapeutic intervention is warranted in most cases.   
• Diagnosis: histopathology is diagnostic.
• Treatment: therapies reported to be successful include topical tacrolimus 0.1%, topical betamethasone, topical hydrocortisone aceponate, topical imiquimod, topical triamcinolone, systemic prednisolone, systemic ciclosporin, systemic interferon, systemic retinoids, and systemic famcyclovir.  Appropriate treatment of any secondary infection.
• Prognosis: good. Spontaneous resolution occurs in most cases.

Presenting signs

• Head-shaking, pruritus and excoriation to both ears. Depression and anorexia accompanied the rapid and dramatic development of proliferative and exudative lesions in the external ear canal . There was a severe, painful, bilateral otitis characterized by erythema, thick and profuse exudation, erosion, ulceration and crusting. Friable material and thick exudation occludes the external ear canals. There was marked submandibular lymphadenopathy and pain on palpation of both ears.
• Lesions are bilaterally symmetrical in most cases and consist of brown-black erythematous and exudative plaques over the medial pinnae and external ear canals. Erosion and ulceration are common as the lesions progress. 
• The lesions are reported to be asymptomatic in most cases but can cause marked pain, depression and anorexia. 
• The lesions that develop in kittens are thought to spontaneously regress in 12-24 months but if causing severe clinical signs, warrant therapeutic intervention.
• Older cats may be more refractory to treatment.

Acute presentation

• Acute onset painful, pruritic bilateral otitis externa.

Geographic incidence

• Unknown.

Age predisposition

• Mainly young cats <1 year of age.

Breed/Species predisposition

• None.

Cost considerations

• When therapeutic intervention is required the cost of therapy should be considered. Oral ciclosporin Ciclosporin and topical tacrolimus Tacrolimus are relatively expensive medications.

Special risks

• General anesthesia is required for biopsy sampling for histopathological diagnosis.