INTRODUCTION: Behçet's disease commonly presents with recurrent oral and genital mucocutaneous ulcerations, uveitis and various skin manifestations. Other clinical symptoms include gastrointestinal ulcerations, arthritis, venous thrombosis, arterial aneurysms and central nervous system affection. Vasculitis underlies most clinical symptoms of Behçet's disease. CASE PRESENTATION: We report the case of a 62-year-old European Caucasian woman with Behçet's disease who presented with persistent fever and neck soft-tissue swelling, despite broad antibiotic treatment, two weeks after acute tonsillitis and a tonsillectomy. Diffuse epi- and mesopharyngeal swelling shown on a computed tomography scan of her neck and persistently elevated serum markers of inflammation initially prompted suspicion of an infectious etiology. Magnet resonance imaging of her neck and a neck tissue biopsy finally confirmed small vessel vasculitis involving skin, subcutaneous tissue and muscle. Considering the clinical presentation, past medical history and histological findings, we interpreted our patient's symptoms as a flare of Behçet's disease. Immunosuppressive treatment led to rapid clinical improvement. CONCLUSION: A patient with Behçet's disease developed small vessel vasculitis of the soft tissue of her neck after tonsillitis and a tonsillectomy. Infection and surgery probably triggered a flare of Behçet's disease.