IgG4-Related Kidney Disease in a Patient With History of Breast Cancer: Findings on 18F-FDG PET/CT.

A 64-year-old African American woman with history of stage III breast carcinoma, 3 years after complete response to therapy, presents with progressive fatigue, increasing arthralgia, and unintentional weight loss of 15 lb in 3 months. An F-FDG PET demonstrated new diffuse FDG avidity of the renal parenchyma, new FDG-avid foci in pancreas and lungs, and new FDG-avid lymph nodes above and below the diaphragm. While a retroperitoneal lymph node biopsy was inconclusive, a kidney biopsy resulted in diagnosis of diffuse, severe, IgG4-related tubulointerstitial nephritis. Treatment with corticosteroid led to complete resolution of the symptoms and PET findings.