A case of middle ear actinomycosis without otalgia that was difficult to diagnose

Abstract

A 22-year-old Japanese male complaining of ear fullness on the left side and pulsatile tinnitus for ten months was referred to our university hospital. The left tympanic membrane was white, swollen, and pulsating. The skin of the external auditory canal was red and swelling. There was no pain. Left conductive hearing loss was observed. Blood test showed no increase in inflammatory response. To diagnose the condition, we performed tympanoplasty. The tympanic cavity was filled with granulation and sulfur granule was observed. Pathological analysis revealed Actinomyces infection in the middle ear. Antibiotic therapy with penicillin for 6 months controlled this infection, and there has been no clinical evidence of infection recurrence for a year since the treatment. Actinomycosis is a very rare disease caused by Gram-positive, anaerobic bacteria of the Actinomyces species. Actinomyces species are difficult to identify through usual bacterial culture methods. To be able to definitively diagnose Actinomyces infection, pathological examination and 16S rRNA gene sequence analysis should be considered.