Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Demonstration of Masticatory Myositis Associated With Behçet’s Disease

A 20-year-old woman with a history of recurrent oral ulcers and acneiform rashes presented with fever, severe trismus, genital ulcers, a positive pathergy test, and laboratory evidence of systemic inflammation. Fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ( ¹⁸ F-FDG PET/CT) demonstrated increased uptake in the masticatory muscles, corroborated by magnetic resonance imaging showing muscle swelling. These findings led to the diagnosis of masticatory myositis associated with Behçet’s disease. Following colchicine therapy, a follow-up ¹⁸ F-FDG PET/CT revealed decreased FDG uptake, correlating with clinical improvement. This case highlights masticatory myositis as a rare cause of trismus in Behçet’s disease, as demonstrated by ¹⁸ F-FDG PET/CT.