LAUSR

A 67-year-old diabetic man was referred for progressive trismus over a period of 4 months. His mouth opening was restricted (Picture A), and his left cheek and masseter muscle were swollen (Picture B, arrowheads). No neoplastic changes were pathologically detected in the masticator tissues. Inflammation of the maxillary sinus had gradually progressed, and enhanced computed tomography (CT) (Picture C) revealed bone destruction (arrowheads) and infiltration around the eyeball (arrows), leading to an ocular motility disorder. Since branching Gram-positive bacteria were detected (Picture D) in the maxillary sinus tissue, with anaerobic culture showing positivity for Actinomyces spp., amoxicillin was administered with a diagnosis of actinomycosis-induced maxillary sinusitis. Bone destruction was inhibited, but fibrotic trismus remained. Actinomycosis is a cause of chronic bacterial infection that results in purulent and granulomatous inflammation (1); however, direct bone and ocular involvement is extremely rare. Given that the clinical course mimics neoplastic involvement (2), actinomycosis should be considered in cases of infiltrating intraoral lesions.