A case of IgG4-related retroperitoneal fibrosis with significant involvement of the abdominal aorta-a clinical and diagnostic challenge.

Immunoglobulin (Ig)G4-related disease (IgG4-RD) with retroperitoneal fibrosis (RPF) is a rare, fibroinflammatory disease involving the soft tissues of the retroperitoneum. A 73-year-old man with IgG4-related RPF affecting the abdominal aorta and iliac arteries was treated with steroids and mycophenolate mofetil. The prevalence of the disease remains unknown because it is often misdiagnosed and can mimic many malignant, infectious, and inflammatory conditions. Autoimmune pancreatitis is a common presenting condition of IgG4-RD. Because As IgG4-RD is responsive to steroids, diagnosing IgG4-related RPF early can prevent the exposure of patients with RPF to unnecessary diagnostic and therapeutic interventions.