IgG4-Related Prostatitis Detected by Whole-Body Diffusion-Weighted Imaging With Background Body Signal Suppression (DWIBS).

IgG4-related disease (IgG4-RD) is a systemic fibro-inflammatory disorder that can affect multiple organs, but involvement of the prostate is rare. Most reported cases of IgG4-related prostatitis are associated with multiorgan disease and present with lower urinary tract symptoms (LUTS). Herein, we present a rare case of IgG4-related prostatitis, which was detected by whole-body diffusion-weighted imaging with background body signal suppression (DWIBS) and was pathologically diagnosed by MRI-fusion target biopsy, accompanied by IgG4-related dacryoadenitis/sialadenitis and multiple lymphadenopathies. Oral prednisolone relieved symptoms including general malaise, weight loss, and LUTS, with decreases in serum IgG4 levels. At the same time, DWIBS showed a remarkable signal reduction in the prostate and other involved organs. The present case suggests the usefulness of DWIBS in detecting and monitoring IgG4-RD including IgG4-related prostatitis.