Autoimmune pancreatitis, also called 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 also called IgG4-related pancreatitis and is part of a disease called IgG4-related disease (IgG4-RD) that often affects multiple organs including the pancreas, bile ducts in the liver, salivary glands, kidneys and lymph nodes.
Type 2 AIP, also called idiopathic duct-centric pancreatitis, seems to affect only the pancreas, although about one-third of people with type 2 AIP have associated inflammatory bowel disease.
Autoimmune pancreatitis is a rare, newly recognized disease and can be mistakenly diagnosed as pancreatic cancer. The two conditions have similar signs and symptoms, but very different treatments, so it is very important to distinguish one from another.
Autoimmune pancreatitis (AIP) is difficult to diagnose. Often, it doesn't cause any symptoms. When it does, its symptoms and signs are similar to those of pancreatic cancer.
Pancreatic cancer symptoms can include:
The most common sign of autoimmune pancreatitis, present in about 80 percent of people, is painless jaundice, caused by blocked bile ducts. AIP can also cause weight loss. Many people with autoimmune pancreatitis have masses in the pancreas and other organs, which can be misdiagnosed as cancer.
Other 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, the body's immune system attacks healthy body tissue.
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 surgery.
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. Until recently, different diagnostic approaches around the world made the diagnosis more difficult. Sometimes, surgery is necessary to exclude pancreatic cancer.
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 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 is easily recognized under a microscope. 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.
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.
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: