Felis ISSN 2398-2950

Ear: proliferative necrotizing otitis externa

Synonym(s): PNOE

Contributor(s): Sarah Warren, Natalie Barnard


  • 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.



  • Idiopathic; possibly immune-mediated (T-cell apoptosis). A viral etiology has also been proposed, but to date viral involvement has not been identified.

Predisposing factors


  • Possibly previous history of otitis, previous viral infection.


  • Usually acute onset of symptoms / clinical presentation.


  • Unknown.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Momota Y, Yasuda J, Arai N et al (2017) Contribution of oral triamcinolone to treating proliferative and necrotising otitis externa in a 14-year-old Persian cat. J Fel Med Surg Open Rep (1), 2055116917691175 PubMed.
  • Momota Y, Yasuda J, Ikezawa M et al (2016) Proliferative and necrotizing otitis externa in a kitten: successful treatment with intralesional and topical corticosteroid therapy. J Vet Med Sci 78 (12), 1883-1885 PubMed.
  • Borio S, Massari F, Abramo F et al (2013) Proliferative and necrotising otitis externa in a cat without pinna involvement: video-otoscopic features. J Fel Med Surg 15 (4), 353-356 PubMed
  • Vidémont E, Pin D (2010) Proliferative and necrotising otitis in a kitten: first demonstration of T‐cell‐mediated apoptosis. JSAP 51 (11), 599-603 PubMed.
  • Mauldin E A, Ness T A, Goldschmidt M H (2007) Proliferative and necrotising otitis in four cats. Vet Dermatol 18 (5), 370-377 PubMed.

Other sources of information

  • Yager J (2009) 22 cases of Proliferative Necrotising Otitis in the cat.  Proceedings of the ESVD Meeting September 2009, Bled, pp 15-20. 
  • Ihrke P J (2008) Breed Based Skin Diseases. Proceedings of the 33rd World Small Animal Veterinary Association and 14th FECAVA. 
  • Gross T L, Ihrke P J, Walker E J, Affolter V K (2005) In: Skin Diseases of the Dog and Cat: Clinical and Histopathologic Diagnosis. Blackwell Scientific.