Autoimmune Pancreatitis

Autoimmune pancreatitis (AIP) is a rare disorder that causes your immune system to attack your pancreas. It triggers ongoing inflammation in your pancreas (pancreatitis), which damages it over time. You might not feel it until it causes significant damage to your pancreas.

Autoimmune disorders happen when your body confuses healthy cells for germs and tries to remove them. AIP can be hard to diagnose. That’s because it’s rare, the symptoms are sometimes vague and findings on imaging can mimic other conditions — particularly, pancreatic cancer. Fortunately, AIP often gets better quickly with the right diagnosis and treatment.

Types of autoimmune pancreatitis

There are two types of autoimmune pancreatitis. They can affect your body in different ways.

Type 1 autoimmune pancreatitis

Type 1 AIP is the most common form. This type is part of a larger autoimmune disorder called IgG4-related disease. IgG4 is an antibody your body produces. It normally blocks other antibodies to dampen immune responses. But if you have type 1 AIP, complexes of IgG4 and another immune cell called plasma cells pass through your pancreas tissue, causing swelling and scarring. It can cause inflammation and damage to many other organs besides your pancreas.

These may include your:

• Bile ducts
• Kidneys
• Liver
• Lungs
• Lymphatic system
• Salivary glands
• Tear ducts
• Thyroid

Most people only have inflammation in some of these parts. Some people only have it in their pancreases. Inflammation in any organ can cause swelling and damage. But not everyone notices any symptoms.

Type 1 AIP is also called:

• IgG4-related AIP: Healthcare providers will detect high levels of IgG4 antibodies in your blood.
• Nonalcohol-related destructive AIP: It affects your pancreas similarly to how alcohol use does.
• Lymphoplasmacytic sclerosing pancreatitis (LPSP): Immune cells (lymphocytes and plasma cells) pass through your pancreas, causing inflammation. The inflammation eventually causes scarring (sclerosis).

Type 1 AIP is more common in males than females by a ratio of 3:1. It tends to develop after age 60.

Type 2 autoimmune pancreatitis

Type 2 AIP doesn’t typically involve high IgG4 levels, and it doesn’t affect other organs. But about 30% of people with type 2 also have inflammatory bowel disease. These conditions are separate but related.

Type 2 may cause repeat episodes of acute pancreatitis. These are times when inflammation increases. You might notice your symptoms more during these times. Then, they might seem to go away.

Type 2 is also called:

• Idiopathic duct-centric chronic pancreatitis (IDCP): “Idiopathic” means it happens for unknown reasons. “Duct-centric” means the inflammation happens mostly inside your pancreatic ducts.
• Granulocyte-positive epithelial pancreatitis: Immune cells called granulocytes trigger the inflammation in type 2 AIP. These cells pass through the lining (epithelium) of your pancreatic ducts.

Type 2 AIP appears at younger ages than type 1. It’s more evenly divided between the sexes.

Symptoms of autoimmune pancreatitis

Autoimmune pancreatitis may not cause symptoms until you’ve had it for a long time. The first symptom to appear is often painless jaundice (a yellow tint to your eyes and skin). Some people also have upper abdominal pain or back pain. This is because your pancreas lies between your stomach and your spine.

Other symptoms can include:

• Dark-colored pee and light-colored poop
• Fatigue
• Indigestion
• Loss of appetite
• Nausea and vomiting
• Unexplained weight loss

You might also have symptoms in other parts of your body, depending on the type of AIP you have.

What causes autoimmune pancreatitis?

Researchers aren’t sure exactly why autoimmune diseases occur. They believe it’s a combination of things. Part of it might be in your genes. But it also involves other, more random factors (environmental factors) that put stress on your immune system. For example, a bad infection might trigger your immune system to overreact. It might get so caught up in fighting it off that it forgets how to stop.

Risk factors

Both types of autoimmune pancreatitis tend to occur more often in people who already have another autoimmune disease. Some of the most common of these include:

• Hashimoto’s disease
• Ulcerative colitis
• Primary biliary cholangitis
• Primary sclerosing cholangitis
• Retroperitoneal fibrosis
• Rheumatoid arthritis
• Sarcoidosis
• Sjögren’s syndrome

Complications of autoimmune pancreatitis

Inflammation that lasts a long time can damage your organs. It causes scar tissue to develop. This stops the blood flow to your organs and stops them from working. Scar tissue in your pancreas can stop it from making the hormones and enzymes your body needs. This can lead to problems with digestion and controlling your blood sugar. Eventually, it can lead to exocrine insufficiency and diabetes.

Other complications can include:

• Biliary stricture: The pipes that drain bile from your liver (bile ducts) run through the head of your pancreas before emptying into your intestine. Inflammation, swelling and scarring in the head of your pancreas can block the part of the bile duct that runs through your pancreas. Because bile can’t empty into your intestine, it seeps out into nearby blood vessels instead, leading to jaundice.
• Pancreatic cancer: People with chronic pancreatitis have a higher risk of developing pancreatic cancer (about 1% to 2%). You might not notice the symptoms because they’re so similar to AIP.

How doctors diagnose autoimmune pancreatitis

It takes a lot of tests to diagnose autoimmune pancreatitis and to figure out which type you have. This is partly because many other conditions can cause the same signs and symptoms. Autoimmune pancreatitis can also look like pancreatic cancer in imaging tests (radiology). So, healthcare providers must look for evidence of AIP in many different ways. Some of these might include:

• Blood tests: Blood tests can check for IgG4 antibodies and markers of pancreatitis, like elevated liver enzymes or elevated pancreatic enzymes. They can also help rule out pancreatic cancer.
• Imaging tests (radiology): An MRI or CT scan can show signs of swelling or scarring in your pancreas and other organs. A special MRI called an MRCP can examine your pancreatic ducts.
• Biopsy: Your provider might need to take a tissue sample from your pancreas or bile ducts to examine in a lab. They can do this through a procedure called an endoscopic ultrasound.
• Treatment trial: Your provider might suggest starting treatment for autoimmune pancreatitis with corticosteroids to see if your condition improves. If it does, it can confirm the diagnosis.

What is the treatment for autoimmune pancreatitis?

Corticosteroids like prednisone or prednisolone treat autoimmune pancreatitis. These medications reduce inflammation and calm your overactive immune system. Treatment usually starts with a high dose of corticosteroids. You’ll gradually lower your dose as your symptoms improve. Your provider might prescribe other immunosuppressant medications to help you wean off corticosteroids.

If you have complications — like narrowing of your bile ducts — you might need other treatments. For example, your provider might need to place a stent to open your bile duct. In some cases, they may need to surgically connect the normal bile duct above your pancreas to your small intestine. This will bypass the obstruction. In other cases, they may recommend surgically removing the affected part of your pancreas. They particularly recommend this when they aren’t sure whether the abnormal imaging findings are due to AIP or cancer.

What’s the prognosis for autoimmune pancreatitis?

Autoimmune pancreatitis usually gets better quickly with treatment. It typically takes just a few weeks of corticosteroids to notice improvement. Many people can eventually stop their medications. But sometimes, symptoms can come back after you stop treatment (relapse). This is more common with type 1 AIP. Some people may need to take corticosteroids for years. Taking them long-term can have side effects.

Your healthcare provider will adjust your treatment plan based on how you respond to it. If you experience relapses or side effects, you might need to try different medications to find a better fit.