Autoimmune Pancreatitis
Autoimmune pancreatitis is an inflammation in the pancreas. It may be caused by the immune system attacking the pancreas. Autoimmune pancreatitis also is called AIP. Two subtypes of AIP are now recognized, type 1 and type 2.
Type 1 AIP is called IgG4-related disease (IgG4-RD). This type often affects multiple organs, including the pancreas, bile ducts in the liver, salivary glands, kidneys and lymph nodes.
Type 2 AIP seems to affect only the pancreas, although about one-third of people with type 2 AIP have associated inflammatory bowel disease.
Type 1 AIP can be mistakenly diagnosed as pancreatic cancer. The two conditions have overlapping symptoms, but very different treatments, so it is very important to distinguish one from the other.
Autoimmune pancreatitis, also called AIP, is difficult to diagnose. Often, it doesn’t cause any symptoms. Symptoms of type 1 AIP are like those of pancreatic cancer.
Pancreatic cancer symptoms can include:
- Dark urine.
- Pale stools or stools that float in the toilet.
- Yellow skin and eyes, called jaundice.
- Pain in your upper belly or middle part of your back.
- Nausea and vomiting.
- Weakness or extreme tiredness.
- Loss of appetite or feelings of fullness.
- Weight loss for no known reason.
The most common sign of type 1 AIP is painless jaundice. About 80% of people with type 1 AIP have painless jaundice. This is caused by blocked bile ducts. People with type 2 AIP can have repeat episodes of acute pancreatitis. Pain in the upper abdomen, a common symptom of pancreatic cancer, is often absent in autoimmune pancreatitis.
Differences between type 1 and type 2 AIP are:
- In type 1 AIP, the disease may affect other organs in addition to the pancreas. Type 2 AIP affects only the pancreas. Type 2 disease also is associated with another autoimmune condition called inflammatory bowel disease.
- Type 1 AIP mostly affects men in the sixth to seventh decade of life.
- Type 2 AIP affects both men and women equally and has a younger age of onset compared with type 1 AIP.
- Type 1 AIP is more likely to relapse after treatment is discontinued.
When to see a doctor
Autoimmune pancreatitis often doesn’t cause any symptoms. See a healthcare professional, however, if you have unexplained weight loss, belly pain, jaundice or other symptoms that bother you.
Experts don’t know what causes autoimmune pancreatitis, but it is thought to be caused by the body’s immune system attacking healthy body tissue. This is known as an autoimmune disease.
The two types of AIP happen with different frequency in different parts of the world. In the United States, about 80% of people with autoimmune pancreatitis, also called AIP, have type 1.
People with type 1 AIP often:
- Are over age 60.
- Are male.
People with type 2 AIP:
- Are often one or two decades younger than those with type 1.
- Are as likely to be female as male.
- Are more likely to have inflammatory bowel disease, such as ulcerative colitis.
Autoimmune pancreatitis can cause a variety of complications.
- Pancreatic exocrine insufficiency. AIP may affect the ability of your pancreas to make enough enzymes. Symptoms may include diarrhea, weight loss, metabolic bone disease, and vitamin or mineral deficiency.
- Diabetes. Because the pancreas is the organ that produces insulin, damage to it may cause diabetes. You may need treatment with oral medicine or insulin.
- Pancreatic and bile duct narrowing, called stricture.
- Pancreatic calcifications or stones.
Treatments for autoimmune pancreatitis, such as long-term steroid use, can cause complications. However, even with these complications, people who are treated for autoimmune pancreatitis have a typical life expectancy.
There is no established association between AIP and pancreatic cancer.
Autoimmune pancreatitis is hard to diagnose, because its symptoms are a lot like those of pancreatic cancer. However, an accurate diagnosis is extremely important. Undiagnosed cancer may result in delaying or not receiving necessary treatment.
People with AIP tend to have a general enlargement of the pancreas, but they also may have a mass in the pancreas. To pinpoint the diagnosis and determine the type of AIP, blood and imaging tests are necessary.
Tests
No single test or characteristic feature identifies autoimmune pancreatitis. Recommended guidelines for diagnosis use a combination of imaging, blood tests and biopsy results.
Specific tests may include:
- Imaging tests. Tests of your pancreas and other organs may include CT, MRI, endoscopic ultrasound (EUS) and endoscopic retrograde cholangiopancreatography (ERCP).
Blood tests. You may have a test to check for elevated levels of an immunoglobulin called IgG4. IgG4 is produced by your immune system. People with type 1 AIP often have high levels of IgG4 in their blood. People with type 2 AIP usually do not.
However, a positive test doesn’t necessarily mean that you have the disease. A small number of people who don’t have autoimmune pancreatitis, including some with pancreatic cancer, also have high levels of IgG4 in their blood.
Endoscopic core biopsy. In this test, a medical professional called a pathologist studies a sample of pancreatic tissue in the laboratory. AIP has a distinctive appearance that can be easily recognized under a microscope by an expert pathologist. A small tube called an endoscope is inserted through the mouth into the stomach, guided by ultrasound. A sample of tissue is then removed from the pancreas using a special needle.
The challenge is getting a sample of tissue large enough to study, rather than just a few cells. This procedure is not widely available, and results may not be conclusive.
- Steroid trial. Autoimmune pancreatitis generally responds to steroids; healthcare professionals sometimes use a trial course of this drug to confirm a diagnosis. However, this strategy should ideally happen under expert guidance. It should be used sparingly and only be done when there is strong evidence to support a diagnosis of autoimmune pancreatitis. Response to corticosteroids is measured by CT and improvement in serum IgG4 levels.
- Biliary stenting. Before starting medicine, sometimes doctors or other healthcare professionals will insert a tube to drain the biliary ducts. This is called biliary stenting and is done in people with symptoms of obstructive jaundice. Often, though, jaundice improves with steroid treatment alone. Sometimes drainage is recommended if the diagnosis is not certain. Tissue samples and cells from the bile duct may be taken at the time of stent placement.
- Steroids. Symptoms of autoimmune pancreatitis often improve after a short course of prednisolone or prednisone. Many people respond quickly, even dramatically. Sometimes people get better without any treatment.
Immunosuppressants and immunomodulators. The disease can relapse. For type 1 AIP, the disease relapses about 30% to 50% of the time. For type 2 AIP, it relapses less than 10% of the time. Cases of relapse require additional treatment, sometimes long term.
To help reduce the serious side effects associated with extended steroid use, medicines that suppress or modify the immune system may be added to the treatment. These are sometimes called steroid-sparing medicines. You may be able to stop taking steroids altogether depending on your response to steroid-sparing medicine.
Immunosuppressants and immunomodulators include mycophenolate (CellCept), mercaptopurine (Purinethol, Purixan), azathioprine (Imuran, Azasan) and rituximab (Rituxan). In general, they have been used in small sample groups and long-term benefits are still being studied.
- Monitoring of other organ involvement. Type 1 AIP often is associated with other organ involvement, including enlarged lymph nodes and salivary glands, scarring of the bile ducts, liver inflammation, and kidney disease. Although these signs may lessen or disappear completely with steroid therapy, your care team will continue to monitor you.
References
- Soliman H, et al. Risk factors and treatment of relapses in autoimmune pancreatitis: Rituximab is safe and effective. United European Gastroenterology Journal. 2019; doi:10.1177/2050640619862459.
- Feldman M, et al., eds. Chronic pancreatitis. In: Sleisenger and Fordtran’s Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, Management. 11th ed. Elsevier; 2021.https://www.clinicalkey.com. Accessed Dec. 1, 2020.
- Whitcomb DC. Autoimmune pancreatitis. https://www.uptodate.com/contents/search. Accessed Dec. 1, 2020.
- Goldman L, et al., eds. Pancreatitis. In: Goldman-Cecil Medicine. 26th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed Dec. 1, 2020.
- Signs and symptoms of pancreatic cancer. American Cancer Society. https://www.cancer.org/cancer/pancreatic-cancer/detection-diagnosis-staging/signs-and-symptoms.html. Accessed Dec. 2, 2020.
- Adam A, et al., eds. The pancreas. Grainger and Allison’s Diagnostic Radiology. 7th ed. Elsevier Limited; 2021. https://www.clinicalkey.com. Accessed Dec. 1, 2020.
- Cameron AM, et al. Unusual pancreatic tumors. In: Current Surgical Therapy. 13th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed Dec. 1, 2020.
- AskMayoExpert. Autoimmune pancreatitis (adult). Mayo Clinic; 2019.
- Ami TR. Allscripts EPSi. Mayo Clinic. Aug. 8, 2023.
- Medical review (expert opinion). Mayo Clinic. Jan. 6, 2021.
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