We report an 18F-FDG linear uptake of the right popliteal artery in a 25-year-old man who underwent a PET/CT scan for unexplained chronic asthenia associated with fever symptoms, arthralgia, and subcutaneous nodes, in favor of vasculitis. The patient had a history of saphenous vein thrombosis. Thrombophilia screening finds a blood lupus anticoagulant. A biopsy of subcutaneous nodes finds an anatomopathologic lesion of polyarteritis nodosa. 18F-FDG PET can be useful in initial staging of polyarteritis nodosa for an early diagnosis of vasculitis, and thus, early treatment can prevent arterial complications such as occlusion or aneurysm.