FDG PET/CT in Sacroiliac IgG4 Disease.

ABSTRACT: A 68-year-old woman with abdominal pain and a raised C-reactive protein was investigated with a CT of the abdomen. CT showed an irregular soft tissue mass anterior to the aorta, which was thought to be neoplastic. The patient underwent 18F-FDG PET/CT, which demonstrated hypermetabolic activity in this mass, as well as further foci of hypermetabolic activity in head and neck, sacroiliac joints, and pelvic floor muscles. A CT-guided biopsy of the sacroiliac joint was performed and revealed IgG4-related disease.