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Evaluating, Diagnosing, and Managing IgG4-RD in Gastroenterology

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Released: October 14, 2026

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IgG4-related disease (IgG4-RD) is a rare, chronic immune-mediated condition that can affect multiple organs and lead to progressive inflammation, fibrosis, and irreversible organ damage. Diagnosing and managing IgG4-RD requires a systematic and multidisciplinary approach to patient care. Learn how IgG4-RD generally presents in gastroenterology, the importance of recognizing multiorgan involvement and ruling out key mimicking diseases, and evidence-based treatment strategies to achieve disease control, prevent relapse, and reduce the risk of irreversible organ damage.

Yasmin G. Hernandez-Barco
Yasmin G. Hernandez-Barco, MD
IgG4RD in gastroenterology

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Autoimmune pancreatitis can be challenging to diagnose and manage in patients with IgG4-related disease (IgG4-RD), particularly because its clinical presentation can overlap with pancreatic cancer and other pancreaticobiliary conditions. It is therefore important for gastroenterology healthcare professionals (HCPs) to distinguish between the different types of autoimmune pancreatitis and recognize pancreatic involvement as part of systemic IgG4-RD. In my practice, I find a systematic approach most helpful by assessing disease involvement beyond the pancreas and considering each patient’s risk of relapse when making treatment decisions.

There are 2 types of autoimmune pancreatitis: type 1 is the pancreatic manifestation of IgG4-RD, and type 2 is an isolated condition that only affects the pancreas. Approximately 33% of type 2 cases are associated with inflammatory bowel disease. These are 2 distinct entities that both respond well to steroid therapy; therefore, diagnosing and treating patients early is critical.

Diagnosing Type 1 vs 2: Looking Beyond the Pancreas:

When evaluating and diagnosing suspected autoimmune pancreatitis, there are several diagnostic and classification criteria to consider, including the International Association of Pancreatology’s International Consensus Diagnostic Criteria, the American College of Rheumatology/European League Against Rheumatism classification criteria for IgG4-RD, and the Mayo Clinic’s HISORt criteria. HISORt stands for histology, imaging, serology, other organ involvement, and response to steroid therapy. I find these criteria helpful as a practical, bedside-type framework for evaluating patients with suspected autoimmune pancreatitis and IgG4-RD.

With the HISORt criteria, for example, a biopsy is not necessarily required in every patient to establish the diagnosis. However, I often obtain a biopsy when a patient presents with a pancreatic mass. In that setting, the goal is not necessarily to confirm autoimmune pancreatitis or IgG4-RD, but rather to rule out malignancy. It is essential to exclude important mimics, particularly when type 1 autoimmune pancreatitis is suspected. Pancreatic cancer and other causes of biliary involvement need to be considered, and primary sclerosing cholangitis and cholangiocarcinoma are also important differential diagnoses.

If a biopsy is performed, it is important not to rely on fine-needle aspiration alone, as it provides cells without preserving the tissue architecture. This distinction is particularly important because pancreatic cancer and other conditions can also have IgG4-positive cells. When tissue is needed, I prefer a core biopsy obtained via endoscopic ultrasound so that the cellular architecture can be evaluated. In type 1 autoimmune pancreatitis, biopsy typically shows dense lymphoplasmacytic infiltrate, storiform fibrosis, obliterative phlebitis, and an elevated ratio of IgG4-positive plasma cells. In contrast, type 2 autoimmune pancreatitis results in a more prominent neutrophil infiltrate that looks incredibly different on biopsy.

Similarly, imaging is a critical tool in the evaluation and diagnosis of autoimmune pancreatitis and IgG4-RD. Although a biopsy may not be necessary in every patient, imaging is essential because it can help identify pancreatic involvement and determine whether there are additional disease manifestations. Characteristic imaging findings of autoimmune pancreatitis often include a hyper enhanced ring around the pancreas, known as a halo sign; an enlarged pancreas with loss of lobulations, sometimes described as a sausage-shaped pancreas; or a very long pancreatic duct stricture without downstream dilation.

Serology is another important part of your evaluation. Although serum IgG4 levels are elevated in approximately 70% of patients with IgG4-RD, they can be elevated in other inflammatory conditions as well. I find IgG4 particularly useful as a biomarker over time when I am fairly confident patients have IgG4-RD. Because those with increased IgG4 levels (eg, greater than 450 mg/dL) at baseline are at high risk for relapse, I want to see their number come down with timely treatment. I will also evaluate and monitor patients’ IgE, total IgG, and complement levels and order CBC, BMP, and liver function tests. In patients with IgG4-RD and biliary involvement and/or elevated liver function tests, trending those tests over time is particularly important for monitoring treatment response.

As I mentioned, a critical step in determining whether patients have type 1 or 2 autoimmune pancreatitis is to assess for extra-organ involvement. If I suspect IgG4-RD in the pancreas or bile ducts, I will also perform a thorough head and neck examination and obtain chest, abdomen, and pelvis imaging, because we must know how many organs are involved at the time of diagnosis. This is especially important considering patients with multiorgan involvement are at higher risk for relapse, which can then change how we approach both induction and maintenance therapy.

Traditional and Emerging Therapies for IgG4-RD:
Finally, response to steroid therapy is the last step for the HISORt criteria. However, HCPs do not necessarily need to prescribe glucocorticoids to confirm a diagnosis of autoimmune pancreatitis or IgG4-RD. In my practice, if a patient presents with a pancreatic mass and I am not completely confident that it is not cancer, I may initiate a trial of prednisone 40 mg and repeat MRI or CT imaging 2-4 weeks after starting glucocorticoid therapy. The mass may not completely disappear, but if it is related to autoimmune pancreatitis rather than cancer, I would expect to see a substantial reduction in its size.

The traditional approach to managing autoimmune pancreatitis and IgG4-RD has been to initiate steroid therapy, monitor for relapse, and then retreat with the potential for bridging to a classic immunomodulator after relapse. However, we now recognize that certain patients with IgG4-RD are at higher risk for relapse, particularly those with multiorgan involvement or elevated baseline IgG4 or IgE levels. Of more importance, each relapse carries the potential for progressive and irreversible damage, particularly to the pancreas and bile ducts.

For these high-risk patients, HCPs should consider additional maintenance therapy to prevent relapse the moment patients are started on a glucocorticoid. Although immunomodulators like azathioprine or mycophenolate mofetil can be considered, I have moved toward B-cell–depleting therapy because of its effectiveness. Inebilizumab is an anti-CD19 monoclonal antibody that is FDA approved for the treatment of IgG4-RD in adults.

Before initiating these therapies, however, it is essential to screen for hepatitis B and C, tuberculosis, and HIV infection and ensure that patients are appropriately vaccinated. I also comanage these patients with rheumatology as part of a multidisciplinary care team to support comprehensive disease management.

Monitoring for Long-term Complications:
IgG4-RD can be indolent, and approximately 60% of patients already have irreversible organ damage at diagnosis. Therefore, in gastroenterology, this means we need to think about both endocrine and exocrine function of the pancreas.

I generally screen patients’ A1C annually. I also ask about any symptoms of exocrine pancreatic insufficiency, including loose or greasy stools, weight loss, and stools that are difficult to flush or wipe. Fecal elastase, which is measured from a solid stool sample, can further serve as a surrogate biomarker of pancreatic function. If symptoms or a low fecal elastase suggest pancreatic insufficiency is present, then pancreatic enzyme replacement can help prevent long-term malnutrition.

Of note, there is no standard interval for repeating lab tests or imaging to assess treatment response or relapse in patients with IgG4-RD. I typically check serum IgG4 every 3 months in patients whose levels are elevated. For patients with a pancreatic mass, I will order repeat imaging at about 4 weeks, 12 weeks, 6 months, and 1 year once resolution is confirmed. For those without a pancreatic mass, I typically repeat imaging at about 3 months.

Regardless of patients having type 1 vs 2 autoimmune pancreatitis, the take-home message is that it and IgG4-RD require a systematic and multidisciplinary approach to prevent irreversible organ damage and relapse.

Your Thoughts:
How often do you consider IgG4-RD as a diagnosis in your patients presenting with autoimmune pancreatitis? You can get involved in the conversation by answering the poll question and posting a comment below.

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