18F-THK5351 PET Findings Indicative of Reactive Astrogliosis in Autoimmune Glial Fibrillary Acidic Protein Astrocytopathy

18F-THK5351 PET visualizes astrogliosis by binding to monoamine oxidase B. Because inflammatory lesions usually accompany astrogliosis, 18F-THK5351 PET can be used as a marker of neuroinflammation. Here we present a case of autoimmune glial fibrillary acidic protein astrocytopathy (GFAP-A) that underwent 18F-THK5351 PET as well as 18F-FDG PET and MRI. 18F-THK5351 PET identified mild inflammatory lesions by imaging astrogliosis, which was difficult for MRI to detect. Although the PET findings were mild, this study suggests that 18F-THK5351 PET may be useful for detecting inflammatory lesions of GFAP-A.