Overview

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.

Symptoms

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.

Causes

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.

Risk factors

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.

Complications

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.

By Mayo Clinic Staff