# Autoimmune Pancreatitis > Autoimmune pancreatitis for NEET-PG Medicine: type 1 and type 2 forms, IgG4 disease, sausage-shaped pancreas and steroid response versus pancreatic cancer. - Canonical URL: https://prepelephant.com/topics/neet-pg/medicine/autoimmune-pancreatitis - Exam / course: NEET-PG · Subject: Medicine - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-14 - Last updated: 2026-10-14 - Reference basis: Harrison's Principles of Internal Medicine; Sherlock's Diseases of the Liver and Biliary System - How to cite: "Autoimmune Pancreatitis", PrepElephant, https://prepelephant.com/topics/neet-pg/medicine/autoimmune-pancreatitis ## Direct answer Autoimmune pancreatitis is a fibro-inflammatory pancreatic disease, usually IgG4-related, that produces a diffusely enlarged, sausage-shaped gland and a long stricture of the main pancreatic duct. Serum IgG4 is often raised, and the bile duct, salivary glands and other organs are frequently involved. Dramatic steroid response helps distinguish it from pancreatic cancer, but malignancy must be reasonably excluded before treatment begins. ## What you must remember - **Type 1 (IgG4-related):** lymphoplasmacytic sclerosing pancreatitis, with raised serum IgG4 in most cases and frequent involvement outside the pancreas. - **Type 2 (idiopathic duct-centric):** granulocytic epithelial lesions in the ducts, usually without raised IgG4, and often coexisting with inflammatory bowel disease. - **Imaging:** diffuse, sausage-shaped enlargement with a halo rim, and MRCP shows a long, narrow stricture of the main duct with little upstream dilatation. - **Extrapancreatic clues:** biliary strictures, sialadenitis, retroperitoneal fibrosis and lacrimal gland involvement point strongly to IgG4 disease. - **Steroid response:** rapid clinical and radiological improvement on corticosteroids supports the diagnosis, but a response alone does not exclude cancer. - **Main mimic:** pancreatic adenocarcinoma, which can cause a focal mass and duct stricture, sometimes needs tissue to settle the diagnosis. - **Relapse:** relapses are common after steroids are tapered, so maintenance with a steroid-sparing agent such as azathioprine is often used. - **Serum IgG4:** a normal level does not exclude autoimmune pancreatitis, particularly in type 2 disease. ## A diagnostic pathway for a diffusely enlarged pancreas Autoimmune pancreatitis is a diagnosis of exclusion as well as of positive features, so the sequence matters. Cancer must be reasonably excluded before steroids are started, because a missed carcinoma is the costliest error. 1. **Suspect the pattern:** Painless obstructive jaundice or a diffusely enlarged pancreas in a middle-aged or elderly patient should prompt autoimmune pancreatitis in the differential. 2. **Check serology:** Measure serum IgG4 and look for other IgG4-related features, remembering that a normal level does not exclude the disease. 3. **Image the gland and duct:** CT or MRCP shows diffuse enlargement, a halo and a long stricture of the main duct, with less upstream dilatation than is typical for cancer. 4. **Seek tissue if uncertain:** Endoscopic ultrasound-guided sampling or ERCP brushings may be needed to exclude carcinoma, and type 1 histology shows a lymphoplasmacytic infiltrate with storiform fibrosis. 5. **Trial steroids cautiously:** Corticosteroids are started once cancer is reasonably excluded and are tapered over several months, with a response within weeks supporting the diagnosis. 6. **Plan maintenance:** Relapse is common, so IgG4 levels and imaging are monitored, and steroid-sparing maintenance is considered when relapses recur. ## Where the exam tries to catch you The exam tests whether you avoid surgery for a benign inflammatory mimic and whether you avoid missing a cancer. - **Trap:** operating on a diffusely enlarged pancreas reflexively — **Correct:** autoimmune pancreatitis responds to steroids, so resection is avoided once cancer is reasonably excluded. - **Trap:** taking a normal IgG4 level as proof of cancer — **Correct:** type 2 disease often has normal IgG4, so tissue and the clinical picture matter more. - **Trap:** assuming a duct stricture always means carcinoma — **Correct:** autoimmune pancreatitis also causes long segmental strictures, which is why imaging is interpreted with the clinical picture. ## Frequently asked questions ### What distinguishes type 1 from type 2 autoimmune pancreatitis? Type 1 is IgG4-related, usually with raised serum IgG4 and disease outside the pancreas. Type 2 is an idiopathic duct-centric form with granulocytic epithelial lesions, which often occurs with inflammatory bowel disease and usually lacks raised IgG4. ### What is the sausage-shaped pancreas sign in autoimmune pancreatitis? A sausage-shaped pancreas is a diffusely enlarged gland with smooth borders, seen on CT or MRI in autoimmune pancreatitis. It contrasts with the focal mass and irregular outline typical of pancreatic adenocarcinoma. ### Why does autoimmune pancreatitis mimic pancreatic cancer? Autoimmune pancreatitis can produce a focal or diffuse mass with a long main duct stricture, which resembles cancer clinically and on imaging. Tissue sampling and the response to steroids help resolve the diagnosis when the picture is uncertain. ### Can steroids be started without a biopsy in autoimmune pancreatitis? Steroids may be started without tissue when imaging and serology are typical and cancer has been reasonably excluded, but this is a clinical judgment. A rapid clinical and radiological response then supports the diagnosis of autoimmune pancreatitis.