We report a 43-year-old man experienced numbness in the distal portion of both legs, which progressed over following two months. Neurological examination showed hypesthesia and muscle weakness in the distal portion of both legs. No abnormal findings were seen on blood test and whole-body contrast enhanced computed tomography (CT). Histopathological findings of the sural nerve and the peroneus brevis muscle showed decreased myelinated nerve fibers with scattered myelin ovoids, vascular occlusion in the epineurium, and inflammatory cell around the arteriole in the muscle bundle. These findings suggested falling in the category as non-systemic vasculitic neuropathy (NSVN). (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) revealed the increase of FDG uptake in the rectum. Inflammatory cell infiltration was found around the arteriole with fibrinoid necrosis in the histopathological specimen of the rectal mucosal biopsy. This result represented the diagnosis as systemic vasculitis. The diagnosis of NSVN may depend on the sensitivity of diagnostic procedure, and (18)F-FDG PET CT might be a useful tool to detect small or medium-sized vasculitis.