# IgG4 Pancreatitis Presenting as a Mass: Unraveling a Diagnostic Illusion

## TL;DR

This paper discusses a rare case of autoimmune pancreatitis that initially appeared as a pancreatic mass, highlighting the diagnostic challenges and successful treatment with steroids.

## Contribution

The novelty lies in presenting a real-world case emphasizing the importance of considering autoimmune pancreatitis in differential diagnosis of pancreatic masses.

## Key findings

- The patient had elevated IgG4 levels and a pancreatic mass, which responded to steroid therapy.
- Autoimmune pancreatitis was confirmed, avoiding misdiagnosis as pancreatic cancer.
- The case underscores the need for thorough evaluation to distinguish autoimmune from malignant conditions.

## Abstract

Autoimmune pancreatitis is a fibroinflammatory subtype of chronic pancreatitis resulting from aberrant immune responses. Currently, there are two forms of autoimmune pancreatitis: type 1 (T1-AIP) or lymphoplasmacytic sclerosing pancreatitis and type 2, also known as idiopathic duct-centric chronic pancreatitis. T1-AIP is often identified as the pancreatic appearance of immunoglobulin 4 (IgG4)-related disease. T1-AIP commonly appears in the seventh decade of life with a considerable male predominance, frequently associated with elevations in serum IgG4 levels and IgG4-positive cells on tissue biopsy. Type 1 and 2 autoimmune pancreatitis glucocorticoid steroid treatment leads to clinical remission in almost 100% of type 1 and 2 cases. Here, we present a case of an adult who presented with an incidental pancreatic head and tail mass on CT imaging with elevated serum IgG4 levels. He was started on steroid therapy with eventual clinical remission of his disease. This case highlights the rarity of autoimmune pancreatitis and the work-up required to rule out malignancy of the pancreatic mass.