Overview
Diagnosis
Autoimmune pancreatitis (AIP) is challenging to diagnose because its symptoms resemble pancreatic cancer. Accurate diagnosis is critical to avoid delayed or inappropriate treatment.
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Imaging tests: CT, MRI, endoscopic ultrasound (EUS), and endoscopic retrograde cholangiopancreatography (ERCP) evaluate the pancreas and surrounding organs. AIP often shows general enlargement of the pancreas, and sometimes a mass.
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Blood tests: Measure IgG4 levels, an antibody produced by the immune system. Type 1 AIP usually shows elevated IgG4, while Type 2 often does not. A positive test alone does not confirm AIP, as some people without the disease, including those with pancreatic cancer, may also have high IgG4.
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Endoscopic core biopsy: A pathologist examines a tissue sample from the pancreas using a special needle guided by an endoscope and ultrasound. AIP has a distinctive microscopic appearance, but adequate tissue sampling can be challenging.
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Steroid trial: Short-term corticosteroid therapy may be used under expert supervision to confirm the diagnosis. Improvement is assessed through CT imaging and IgG4 blood levels.
Treatment
Treatment aims to reduce inflammation, relieve symptoms, and prevent relapse.
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Biliary stenting: Sometimes used for obstructive jaundice to drain the bile ducts before or during treatment. Tissue or cell samples may also be taken during this procedure.
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Steroids: Prednisolone or prednisone is often highly effective, and many people respond quickly. In some cases, symptoms improve without treatment.
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Immunosuppressants and immunomodulators: Relapse occurs in 30–50% of Type 1 AIP cases and <10% in Type 2. Steroid-sparing medicines, such as mycophenolate (CellCept), mercaptopurine (Purinethol, Purixan), azathioprine (Imuran, Azasan), or rituximab (Rituxan), may be used to reduce long-term steroid side effects and maintain remission.
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Monitoring other organ involvement: Type 1 AIP may involve enlarged lymph nodes, salivary glands, bile duct scarring, liver inflammation, or kidney disease. These may improve with steroids, but ongoing monitoring is needed.
Early treatment and careful follow-up improve outcomes and reduce complications. Relapses are treated promptly with steroids or immunomodulators to maintain pancreatic and overall health.
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