Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) is inflammation of the pancreas caused by the immune system mistakenly attacking the organ. Two subtypes of AIP are recognized: type 1 and type 2.

Type 1 AIP, also called IgG4-related disease (IgG4-RD), can affect multiple organs, including the pancreas, bile ducts, salivary glands, kidneys, and lymph nodes. Type 2 AIP typically affects only the pancreas, although about one-third of people with type 2 have inflammatory bowel disease.

Type 1 AIP can be mistaken for pancreatic cancer because the two conditions share similar symptoms, but treatments differ significantly. Accurate diagnosis is important for proper management.

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Symptoms

Autoimmune pancreatitis can be difficult to diagnose, and some people have no symptoms. Type 1 AIP symptoms resemble those of pancreatic cancer, including:

• Dark urine

• Pale or floating stools

• Yellowing of skin and eyes (jaundice)

• Upper abdominal or back pain

• Nausea and vomiting

• Weakness or extreme tiredness

• Loss of appetite or early feelings of fullness

• Unexplained weight loss

The most common sign of type 1 AIP is painless jaundice caused by blocked bile ducts, affecting about 80% of patients. Type 2 AIP may present with recurrent acute pancreatitis, but abdominal pain is often absent.

Differences between type 1 and type 2 AIP include:

• Type 1 can affect other organs, while type 2 is limited to the pancreas and often associated with inflammatory bowel disease

• Type 1 mostly affects men aged 60–70, while type 2 affects men and women equally and has a younger onset

• Type 1 is more likely to relapse after treatment is stopped

When to see a doctor

Consult a healthcare professional if you experience unexplained weight loss, abdominal pain, jaundice, or other concerning symptoms. Early evaluation helps ensure proper diagnosis and treatment.

Causes

The exact cause of autoimmune pancreatitis is unknown. It is thought to result from the immune system attacking healthy pancreatic tissue, classifying it as an autoimmune disease.

Risk factors

Risk factors vary depending on AIP type:

• Type 1 AIP: More common in men over age 60

• Type 2 AIP: Occurs in younger adults, affects men and women equally, and is often associated with inflammatory bowel disease such as ulcerative colitis

Complications

Autoimmune pancreatitis can lead to several complications:

• Pancreatic exocrine insufficiency, affecting enzyme production and causing diarrhea, weight loss, metabolic bone disease, and vitamin or mineral deficiencies

• Diabetes, due to pancreatic damage affecting insulin production, which may require oral medications or insulin therapy

• Narrowing of the pancreatic and bile ducts (stricture)

• Pancreatic calcifications or stones

Long-term treatments, such as steroid therapy, can also cause complications. Despite these issues, people treated for AIP generally have a typical life expectancy. There is no established link between autoimmune pancreatitis and pancreatic cancer.

Prevention

There is no known way to prevent autoimmune pancreatitis. Early diagnosis and appropriate treatment can help manage symptoms, prevent organ damage, and reduce the risk of complications.