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E1159. Not Just Autoimmune Pancreatitis: Spectrum of IgG4-Related Disease in the Abdomen and Pelvis
Authors
  1. Sonam Jaglan; NYU Langone
  2. Jay Karajgikar; NYU Langone
Background
Until 2003, the role of IgG4-plasma cell mediated disease was only understood in the context of type 1 autoimmune pancreatitis. Since then, there has been increasing awareness of a spectrum of disorders affecting various organ systems throughout the body with a common root cause falling under the umbrella of IgG4-related disease (IgG4-RD). This immune-mediated condition involves the infiltration of IgG4-positive plasma cells into various organs resulting in fibrosis and tumefactive lesions, with elevated serum IgG4 concentrations found in most patients. In addition to the pancreas, manifestations of IgG4-RD have been described in numerous organs including the biliary tree, gallbladder, kidneys, lungs, mesentery, retroperitoneum, breasts, prostate, thyroid, skin, and head and neck. While the definitive diagnosis of IgG4-RD involves characteristic imaging, hematologic, and histopathologic findings, the diagnosis is often first suggested on the basis of imaging. Adding to the difficulty in making the diagnosis is the generally mild and nonspecific clinical presentation of the patient, often mimicking malignancy. As patients with IgG4-RD respond well to steroid therapy, awareness and knowledge of this entity is key for the radiologist, who often may be the first to suggest it. Delay in the appropriate diagnosis of IgG4-RD can lead to end-organ damage as well as unnecessary work-up and possible surgery for other conditions which have similar appearances on imaging. The clinical diagnosis of IgG4-RD remains a challenge often requiring multidisciplinary contribution, and radiologists play a critical role in suggesting and establishing the diagnosis. The purpose of this educational exhibit is to review the classic imaging manifestations of IgG4-RD in the abdomen and pelvis and to provide helpful clues which may suggest this entity over more commonly encountered pathology.

Educational Goals / Teaching Points
1. To review the characteristic abdominopelvic imaging findings of IgG4-RD. 2. To review classic IgG4-RD mimics and differential considerations. 3. To provide helpful clues which may help favor IgG4-RD over other differential considerations as well as pitfalls in the diagnosis.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
This exhibit is a case-based review of imaging manifestations of IgG4-RD in the abdomen and pelvis. CT, MR, and ultrasound imaging will be used to demonstrate known manifestations of IgG4-RD in the pancreas, kidneys, biliary tree, mesentery, bowel, retroperitoneum, and thyroid. Additionally, the exhibit will provide examples of other similar-appearing entities in the differential diagnosis (i.e., malignancy, infection, vascular etiologies) and provide clues to prevent potential diagnostic pitfalls.

Conclusion
The diagnosis of IgG4-RD remains a challenge in which radiologists have a vital role to play. Often the radiologist is first to suggest the diagnosis, helping to potentially prevent unnecessary treatment, workup, and even surgical intervention. This educational exhibit reviews the imaging findings of IgG4-RD in the abdomen and pelvis and highlights mimics and pitfalls radiologists may face when encountering these cases.