Actinomycosis is a rare, chronic and slowly progressive granulomatous disease, caused by Gram-positive, anaerobic bacteria of the Actinomyces species. The most common site of Actinomyces infection is the cervicofacial region, and actinomycosis of the middle ear and mastoid is very rare. Herein, we report a case of actinomycosis of the middle ear and mastoid, diagnosed from the histopathological features of specimens collected from the middle ear through exploratory tympanotomy.
A 46-year-old man presented to our hospital complaining of otorrhea and hearing loss on the left side, which failed to improve with antibiotic treatment for 9 months. Otoscopic examination revealed reddishness and thickening of the tympanic membrane. Pure tone audiometry showed moderate mixed hearing loss in the left ear. Histopathological examination of the middle ear specimen collected through myringotomy revealed inflammatory granulation tissue, consistent with the findings of computed tomography and magnetic resonance imaging of the temporal bone. Bacterial culture of the otorrhea fluid did not reveal any pathogens. He was treated with antibiotics for three weeks, but his condition failed to improve. Finally, we decided to perform exploratory tympanotomy, and found yellow granules surrounded by granulation tissue in the tympanic cavity. Histopathological examination of the granules revealed Gram-positive bacterial colonies, consistent with the diagnosis of actinomycosis. The patient was treated with penicillin for 1 year, with improvement. There has been no sign of recurrence since.
Difficulty in diagnosing actinomycosis by bacterial culture of the specimen is attributable to the fact that Actinomyces species are hard to grow on agar plates. In almost all the reported cases, the diagnosis of actinomycosis was made by histopathological examination of appropriate specimens. In case where otitis media fails to improve with antibiotic administration, clinicians should suspect actinomycosis and collect middle ear specimens for the diagnosis.
