Autoimmune pancreatitis: type 1 (IgG4-related) vs type 2
- Lesion
Autoimmune pancreatitis is an immune swelling of the pancreas that can look like cancer but improves with corticosteroids.
What it is
Autoimmune pancreatitis is a form of chronic pancreatitis with dense lymphoplasmacytic inflammation and fibrosis that often forms a mass and mimics pancreatic cancer. Type 1 is the pancreatic manifestation of IgG4-related disease, usually in older men, with raised serum IgG4 and other organ involvement. Type 2 occurs in younger patients, is limited to the pancreas, is linked to inflammatory bowel disease and shows neutrophils destroying ducts. Both respond to corticosteroids.
Step by step
- An immune response, not fully understood, targets pancreatic ducts and acini.
- Type 1: Th2 and regulatory T cells drive IgG4-producing plasma cells and fibroblasts.
- Type 2: neutrophils attack duct epithelium.
- Dense inflammation and fibrosis enlarge the gland and narrow ducts and the bile duct.
- Corticosteroids suppress the infiltrate and the gland shrinks.
Type 1 vs type 2 autoimmune pancreatitis
| Feature | Type 1 (IgG4-related) | Type 2 |
|---|---|---|
| Patients | Older, mostly men | Younger, both sexes |
| Serum IgG4 | Often raised | Normal |
| Histology | IgG4 plasma cells, storiform fibrosis, obliterative phlebitis | Neutrophils in duct epithelium (granulocytic epithelial lesion) |
| Other organs | Bile ducts, salivary glands, kidney, retroperitoneum | Pancreas only; inflammatory bowel disease |
| Relapse | Common | Rare |
Markers
- IgG4 immunostain
- Serum IgG4
Test yourself
Think of the answer, then tap the question to see it.
Which histologic features define type 1 autoimmune pancreatitis?
Many IgG4-positive plasma cells, storiform fibrosis and obliterative phlebitis.
What is the granulocytic epithelial lesion?
Neutrophils infiltrating and destroying duct epithelium, the hallmark of type 2 autoimmune pancreatitis.
Why is autoimmune pancreatitis important to recognize?
It can mimic pancreatic carcinoma but responds to corticosteroids, so surgery may be avoided.
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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Chronic Pancreatitis (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.