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# 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.

Updated Nov 12, 2026

## Key points

- Type 1: IgG4-positive plasma cells, storiform fibrosis, obliterative phlebitis; serum IgG4 often high; other organs (bile ducts, salivary glands, kidney, retroperitoneum).
- Type 2: granulocytic epithelial lesion (neutrophils in duct epithelium); IgG4 normal; associated with ulcerative colitis.
- Imaging: diffuse 'sausage-shaped' enlargement or a focal mass.
- Key differential: pancreatic adenocarcinoma.
- Both types respond to corticosteroids; type 1 relapses more.

## 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

## Memory aid

Type 1 is the IgG4 'old man' with many organs; type 2 is the young colitis patient with neutrophils in the ducts.

## 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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## Elsewhere in DurgiPedia

- [Immune tolerance and how autoimmunity begins](https://durgical.com/en/immunology/immune-tolerance-and-how-autoimmunity-begins/)

## Connections

## Related 5

- [Chronic pancreatitis: fibrosis, ductal stones and lost acini](https://durgical.com/en/general-pathology/chronic-pancreatitis-fibrosis-ductal-stones-and-lost-acini/)
- [Pancreatic ductal adenocarcinoma](https://durgical.com/en/general-pathology/pancreatic-ductal-adenocarcinoma/)
- [Primary sclerosing cholangitis](https://durgical.com/en/general-pathology/primary-sclerosing-cholangitis/)
- [Chronic inflammation: causes, cells and features](https://durgical.com/en/general-pathology/chronic-inflammation-causes-cells-and-features/)
- [Fibrosis in organs: TGF-β and the myofibroblast](https://durgical.com/en/general-pathology/fibrosis-in-organs-tgf-and-the-myofibroblast/)

## Related conditions 4

- [IgG4-related disease](https://durgical.com/en/conditions/igg4-related-disease/)
- [Chronic pancreatitis](https://durgical.com/en/conditions/chronic-pancreatitis/)
- [Pancreatic cancer](https://durgical.com/en/conditions/pancreatic-cancer/)
- [Ulcerative colitis](https://durgical.com/en/conditions/ulcerative-colitis/)

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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](https://www.ncbi.nlm.nih.gov/books/NBK482325/) (StatPearls (NCBI Bookshelf), 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/autoimmune-pancreatitis-type-1-vs-type-2/