Immunoglobulin G - 4(IgG4)-related disease: A case of retroperitoneal disease with mass formation

IgG4-related disease is a rare cause of retroperitoneal fibrosis with mass formation. A 46-year-old female presented with lower back pain. She had an on-and-off mild fever and constitutional symptoms with evidence of tenderness over the lower back. Investigations revealed high inflammatory markers. Magnetic resonance imaging revealed an ill-defined signal area in the left paraspinal area. Histology revealed fibromuscular tissue with scattered plasma cells showing positivity for immunoglobulin-G-4 (IgG4). The immunomorphological features are suggestive of IgG4-related-retroperitoneal fibrosis. She was commenced on glucocorticoids. It is imperative to consider unusual diagnoses such as IgG4-related disease in a patient with retroperitoneal disease with evidence of mass formation.