Autoimmune pancreatitis is a relatively uncommon disease of the pancreas that may be mistaken for pancreatic cancer.
Autoimmune pancreatitis (AIP) is a chronic inflammation that is thought to be caused by the body's immune system attacking the pancreas and that responds to steroid therapy. Two subtypes of AIP are now recognized, type 1 and type 2.
Type 1 AIP is the pancreatic manifestation of a disease called IgG4-related disease (IgG4-RD). This disease 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 signs and symptoms, but very different treatments, so it is very important to distinguish one from the other.
Autoimmune pancreatitis (AIP) is difficult to diagnose. Often, it doesn't cause any symptoms. Symptoms and signs of type 1 AIP are similar to those of pancreatic cancer.
Pancreatic cancer signs and symptoms can include:
The most common sign of type 1 AIP, present in about 80% of people, is painless jaundice, caused by blocked bile ducts. Type 2 AIP can present with recurrent episodes of acute pancreatitis. Pain in the upper abdomen, a common symptom of pancreatic cancer, is frequently absent in autoimmune pancreatitis.
Differences between type 1 and type 2 AIP are:
Autoimmune pancreatitis often doesn't cause any symptoms. See your doctor, however, if you experience unexplained weight loss, abdominal pain, jaundice, or other signs and symptoms that bother you.
Doctors don't know what causes autoimmune pancreatitis, but as in other autoimmune diseases, it is thought to be caused by the body's immune system attacking healthy body tissue.
The two types of AIP occur with different frequency in different parts of the world. In the United States, about 80 percent of people with autoimmune pancreatitis have type 1.
People with type 1 autoimmune pancreatitis often:
People with type 2 autoimmune pancreatitis:
Autoimmune pancreatitis can cause a variety of complications.
Treatments for autoimmune pancreatitis, such as long-term steroid use, also can cause complications. However, even with these complications, people who are treated for autoimmune pancreatitis have a normal life expectancy.
There is no established association between AIP and pancreatic cancer.
Autoimmune pancreatitis is difficult to diagnose, because its signs and symptoms are very similar to 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 may also have a mass in the pancreas. To pinpoint the diagnosis and determine which type of AIP you have, blood and imaging tests are necessary.
No single test or characteristic feature identifies autoimmune pancreatitis. Consensus guidelines for diagnosis use a combination of imaging, blood tests and biopsy results.
Specific tests may include:
Blood tests. You will be tested for elevated levels of an immunoglobulin called IgG4, produced by your immune system. People with type 1 AIP, but usually not with type 2 AIP, will have highly elevated blood levels of IgG4.
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 blood levels of IgG4.
Endoscopic core biopsy. In this test, pathologists analyze 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. Doctors insert a small tube (endoscope) through the mouth into the stomach and, guided by ultrasound, remove some tissue from the pancreas using a special needle.
The challenge is obtaining a sample of tissue large enough to analyze, rather than just a few cells. This procedure is not widely available, and results may not be conclusive.
Immunosuppressants and immunomodulators. About 30% to 50% of the time in type 1 AIP and less than 10% of the time in type 2 AIP, the disease relapses, requiring additional treatment, sometimes long term.
To help reduce the serious side effects associated with extended steroid use, doctors often add drugs that suppress or modify the immune system, sometimes called steroid-sparing medications, to the treatment. You may be able to stop taking steroids altogether depending on your response to steroid-sparing medication.
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.
Start by seeing your primary care doctor if you have signs or symptoms that worry you. If your doctor suspects you may have autoimmune pancreatitis, you may be referred to a gastroenterologist or a pancreatologist.
Your time with the doctor is limited. You may feel less rushed if you make a list of questions you want to ask at your appointment. Here are some possible questions about autoimmune pancreatitis:
In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask questions that come up during your appointment.
Your doctor is likely to ask you a number of questions. Being ready to answer them may allow more time later to cover points you want to address. Your doctor may ask: