Keratosis obturans is a rare external auditory canal (EAC) disease characterised by abnormal accumulation and consequently occlusion and expansion of the bony portion of the EAC by a plug of desquamated keratin. It can be confused for EAC cholesteatoma but they are completely different entities requiring different treatment.

Epidemiology

Keratosis obturans is seen in younger patients usually less than 40 years old and is bilateral in 50% of cases.

Clinical presentation

Patients present with acute severe pain and conductive hearing loss.

Pathology

The cause is not clear in the majority of cases.

Keratosis obturans is characterised by:

• dense plug of keratin debris within the deep meatus

• hyperplasia of the underlying epithelium

• chronic inflammation within the subepithelial tissue

• remodelling and expansion of the canal

• no evidence of erosion or necrosis of the underlying bone

Associations

• bronchiectasis

• chronic paranasal sinus disease

NB particularly in the paediatric group, where these concurrent findings approach 80%; but only in 20% of adult patients.

Radiographic features

CT

• well-defined soft tissue mass within the bony EAC which may diffusely enlarge the canal with no bony erosion, as opposed to EAC cholesteatoma

• tympanic canal is usually spared but may be slightly thickened

Treatment and prognosis

Usually treated by EAC toilet; due to a high incidence of recurrence, it may require several excisions of keratin plugs. It rarely needs surgical intervention.

Differential diagnosis

• external auditory canal debris, which partially fills the EAC and usually shows air foci

• external auditory canal cholesteatoma: EAC soft tissue density with bony erosion

• external auditory canal carcinoma: irregular mass with or without bony erosion

• otitis externa: surrounding inflammatory fat stranding

• epidermal inclusion cyst of the external auditory canal