Mass-forming Autoimmune Pancreatitis (AIP) mimicking a pancreatic head lesion
Siobhan Alsop, University Hospitals Plymouth NHS Trust
Introduction
This report describes a case of mass-forming autoimmune pancreatitis (AIP), of which I wish to share my learning and experience.
Case
A 57-year-old female was referred for abdominal ultrasound for fatigue, painless jaundice and abnormal liver function tests. She was not tender on assessment. Ultrasound demonstrated a solid pancreatic head mass, isoechoic to the pancreas, with no biliary dilatation. The appearances and presentation were suspicious for malignancy, and consultant review prompted 2-week-wait referral for CT staging. Pancreatitis was not suspected. CT was negative for cancer but demonstrated enlargement and loss of definition of the pancreatic clefts, suggestive of AIP. Correlation with elevated serum immunoglobulin G4 (IgG4) confirmed the diagnosis. MRI was performed eight weeks later to review response to steroidal treatment, which was unsuccessful. The patient was referred for immunosuppressant control, and will undergo annual imaging surveillance. She experiences ongoing fatigue but is otherwise well. AIP is an organ-specific manifestation of systemic IgG4 disease, categorised by serum IgG4 elevation1. There can be multiple organ involvement affecting structures such as the kidneys and lungs. AIP is a mimicker of pancreatic and biliary neoplasia, often presenting with painless jaundice. The isoechoic appearance of the inflammatory mass and nil duct dilatation may have served a clue to the aetiology, although this can be seen in malignant and inflammatory disease. Cross-sectional imaging is always indicated for characterisation; however, an awareness of AIP and painless inflammatory masses as differentials for malignancy will enable sonographers to report helpful, differential diagnoses which may alter or improve management, and reduce undue patient anxiety.
Conclusions
Sonographers should be mindful that pancreatitis is a complex disease with a range of aetiologies and manifestations beyond gallstones and epigastric pain. Pancreatic masses may be inflammatory in origin and conditions such as AIP are often painless mimickers of malignancy.