IgG4-related disease and isolated retroperitoneal fibrosis: A narrative review.

Retroperitoneal fibrosis (RPF) can occur due to many etiologies and is categorized into idiopathic and secondary. Etiologies of secondary RPF include medications, autoimmune disease, malignancy, and IgG4-related disease (IgG4-RD). Although IgG4-RD usually involves multiple systems synchronically including the pancreas, aorta, and kidneys, it can present with isolated RPF without involvement of other organ systems. Caution must be exercised in these instances as the diagnosis should be confirmed based on specific clinical, radiographic, and histopathologic criteria. Such confirmation can affect the work-up and therapeutic approach as treatment with corticosteroids can lead to remission, both clinically and radiographically.