The Diagnostic Challenges of Autoimmune Pancreatitis – A Case Report

Abstract

Purpose: Autoimmune pancreatitis (AIP) is a fibro-inflammatory disease that accounts for 4,6–5,0% of chronic pancreatitis and encompasses two entities, one related to a systemic disease referred to as IgG4-related disease (type 1 AIP) and the other generally without immunoglobulin G4-positive cells and without systemic involvement (type 2 AIP). Its association to other autoimmune diseases, namely ulcerative colitis, is known although the exact relationship between the two entities is not completely clarified. The diagnosis of autoimmune pancreatitis requires a multidisciplinary approach. Due to overlap in clinical and radiological features, it is often misdiagnosed as pancreatic cancer. Methods and Aims: This clinical case report describes an uncommon entity highlighting the challenge in the diagnostic approach of a pancreatic mass. Results: A 45-year-old female, with a medical history of ulcerative colitis and arterial hypertension treated with bisoprolol and mesalazine, underwent an abdominal computerized tomography scan (CT scan) for study of a solid liver lesion, which incidentally revealed a tail pancreatic mass. There were no symptoms at all and physical examination was normal. Laboratory analyses showed normal levels of immunoglobulin G4 and negative antinuclear antibodies. Endoscopic ultrasound revealed a homogeneous and hypoechogenic lesion in the pancreatic tail with a “sausage-like” appearance. Endoscopic ultrasound-guided fine needle aspiration was inconclusive (pancreatic adenocarcinoma hypothesis could not be excluded) and the patient underwent a laparoscopic distal pancreatectomy. Histopathology examination confirmed the diagnosis of a type 2 autoimmune pancreatitis. At 12-month follow-up, the patient remained asymptomatic with no evidence of recurrence. Conclusions: The diagnosis of AIP is a clinical challenge, not only due to its rarity, but also due to the need of integrating clinical, laboratory, imaging, and histology data for confirmation. Although the diffuse form of AIP can be easily distinguished from pancreatic cancer on imaging, differentiating focal AIP from pancreatic malignancy is challenging, so a surgical approach is often proposed. The association of AIP with other autoimmune illnesses can be identified in more than half of the cases. Among these, the association with inflammatory bowel disease, and more specifically with ulcerative colitis, has been described being the most common.