18F-fluorodeoxyglucose-positron emission tomography scanning is a useful tool for therapy evaluation of arterial aneurysm in Behçet's disease.

[(18)F]fluorodeoxyglucose-positron emission tomography (FDG-PET) has demonstrated its usefulness in giant cell arteritis, Takayasu's arteritis, and unclassified aortitis. FDG-PET imaging could be more effective than CT-scan or magnetic resonance imaging in detecting the earliest stages of vascular wall inflammation. Data are lacking regarding its accuracy for diagnosis and follow-up of vascular lesions in Behçet's disease. We report the case of a 32-year-old woman with history of Behçet's disease and fever of unknown origin revealing voluminous pulmonary arterial aneurysms. FDG-PET scan revealed a peripheral uptake of pulmonary aneurysms, underlying the inflammatory status of arterial aneurysms wall. Our patient was treated by glucocorticoids and intravenous cyclophosphamide and achieved remission of Behçet's disease. During follow-up, FDG-PET scan enabled to detect an early radiologic therapeutic response after 4 months, while CT angiography remained unchanged. We report the first evidence of usefulness of FDG-PET scan for therapeutic evaluation of arterial aneurysms in Behçet's disease. Further studies are warranted to determine the accuracy of FDG-PET scan in larger cohort of Behçet's disease patients with vascular involvement.