<p>There are few published reports about keratosis obturans (external auditory canal cholesteatoma), and the pathogenesis and diagnostic criteria remain unclear. Herein, we report a rare pediatric case of keratosis obturans who presented with severe otalgia. The patient was a 7-year-old girl with a 4-year history of intermittent otalgia for which she had been receiving treatment from a local doctor. She had been diagnosed as having parotitis and otitis externa. However, in the 6 months prior to her first visit to our department, her pain had become more severe, failed to be controlled even with painkillers, and she had begun to cry repeatedly at night. Examination revealed that her right ear canal was filled with cerumen and ear discharge, but she failed to cooperate for a more detailed examination. Thus, we were unable to treat her adequately at first. A temporal bone CT showed a soft shadow filling the external auditory canal, middle ear, and mastoid, and extensive destruction of the bony external auditory canal. Based on the findings, we made the diagnosis of keratosis obliterans (external auditory canal cholesteatoma). We treated the patient by endoscopic ear surgery performed under general anesthesia 9 days after her first visit to our department. The otalgia resolved and she stopped crying at night immediately after the surgery. Until date, 18 months since the surgery, the ear canal has remained self-cleaning. Keratosis obliterans is a disorder in which the self-cleaning function of the external auditory canal is impaired and cornified epithelium accumulates in the external auditory canal, resulting in pressure dermatitis. No diagnostic criteria have been established to clearly distinguish this condition from external auditory canal cholesteatoma. There is no consensus on the treatment of external auditory canal cholesteatoma. Surgical treatment is considered as being indicated in children when bone destruction is extensive, when there is infection caused by resistant bacteria that is refractory to treatment, when the external auditory canal is narrowed, and when there is no improvement in response to outpatient treatment. We report this patient to underscore the need for caution against a delay in the diagnosis which could lead to severe complications.</p>