Abstract
A 71-year-old Japanese man who had elevated serum immunoglobulin G4 (IgG4) levels presented with periarteritis of the left external iliac artery. Whole body fluorodeoxyglucose positron emission tomography/computed tomography revealed abnormal uptake at the left external iliac artery (maximum standardized uptake value 4. 4), subcarinal lymph nodes (maximum standardized uptake value 6.4), and prostate (maximum standardized uptake value 5.7). Laboratory examination showed high serum IgG4 l and normal prostate-specific antigen levels. A needle biopsy of the prostate was performed. The histopathological examination revealed carcinoma, but did not show lymphoplasmacytic infiltration. A biopsy of the subcarinal lymph nodes with transbronchial biopsy was also performed, and the histopathological examination did not find infiltration of plasma cells or malignant cells. During evaluation, hydronephrosis was indicated by increased soft tissue shadows around the left external iliac artery. After three months of hormone therapy for prostate cancer, the soft tissue shadows decreased, and the hydronephrosis disappeared. The levels of serum IgG4 did not change during the treatment. The periarteritis was considered a paraneoplastic syndrome of prostate cancer.