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 seems to affect only the pancreas, although about one-third of people with type 2 AIP have associated inflammatory bowel disease.
Both subtypes of autoimmune pancreatitis are treated with steroids, which in many people dramatically improve the condition.
Autoimmune pancreatitis is a rare, newly recognized disease and can be mistakenly diagnosed as pancreatic cancer. Both 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 very similar to those of pancreatic cancer.
Pancreatic cancer symptoms can include:
- Dark urine
- Pale stools or stools that float in the toilet
- Yellow skin and eyes (jaundice)
- Pain in your upper abdomen 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 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.
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:
- Are over age 60
- Are male
- Have multiple organ involvement including the bile ducts (IgG4-related sclerosing cholangitis), the salivary glands (IgG-related sialadenitis), or the lungs (IgG4-related pulmonary disease)
- Have retroperitoneal fibrosis (RPF), which is the formation of extra fibrous tissue in the area behind the stomach and intestine
- Have lymph node enlargement (lymphadenopathy), low thyroid (hypothyroidism) or kidney disease
People with type 2 autoimmune pancreatitis:
- Are often over age 40 (one or two decades younger than those with type 1)
- Are as likely to be female as male
- Have a 30 percent chance of having inflammatory bowel disease, such as ulcerative colitis
When to see a doctor
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 can cause a variety of complications.
- Pancreatic insufficiency. AIP may affect the ability of your pancreas to make enough enzymes. Signs and 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, and you may need treatment with oral medication or insulin.
- Pancreatic calcifications or stones.
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.