C0071 - Mind the Gap: A Case of Autoimmune Pancreatitis

Jonathan D. Hickman, DO¹, Melissa Lee, DO², Brett Sadowski, MD^2
1Naval Medical Center Portsmouth, Norfolk, VA; ²Naval Medical Center Portsmouth, Portsmouth, VA

Introduction: Autoimmune pancreatitis (AIP) classically presents as painless jaundice, similar to its mimicker pancreatic cancer, but it can also present in other manifestations to include abdominal pain, weight loss, steatorrhea or even cholangitis. The diagnosis and distinction between AIP and pancreatic cancer is often very difficult even beyond clinical presentation and despite utilization of laboratory analysis and imaging, it is estimated that around 30% of AIP cases require core biopsy, steroid trial, or surgery to make definitive diagnosis. Additionally, the high mortality associated with pancreatic cancer without treatment can spear-head more aggressive treatment.

Case Description/Methods: We present a case of a 63 year old male who underwent workup for postprandial abdominal pain and mild elevation of liver associated enzymes with normal bilirubin. He then had an MRI, which showed an irregular pancreatic head mass suspicious for malignancy that was further analyzed via EUS and biopsy showing atypia but no definite evidence of adenocarcinoma. Tumor markers showed elevation of CA 19-9. He was referred to an oncologist and the decision was made that this was most likely pancreatic cancer. He was initiated on modified folfirinox and radiation therapy which led to reduction in size of the mass on repeat imaging. The patient eventually underwent pancreaticoduodenectomy. Labs after his surgery did not improve and actually worsened in both cholestatic and hepatocellular patterns. The specimen demonstrated storiform fibrosis and lymphoplasmacytic infiltrate consistent with HISORt type 1 AIP as well as positive IgG4 staining. After referral to tertiary care center GI, an IgG4 level was found significantly elevated, consistent with AIP in addition to autoimmune cholangiopathy. He had a robust response to steroids and eventually transitioned to rituximab with significant improvement in his clinical and biochemical markers.

Discussion: The persistent elevation in this patient’s protein gap likely represented his elevated IgG4 level and may have been a clue to the diagnosis well before this patient’s interventions. Ultimately, diagnosis is made with the HISORt criteria. It has been proposed utilizing a combination of IgG4 and CA 19-9 to distinguish AIP from pancreatic carcinoma with CA19-9 < 74 and IgG4 >1.0 showing a 100% PPV and a 96% NPV. This case demonstrates the importance of considering AIP during evaluation of pancreatic head mass to avoid delayed diagnosis, unnecessary treatment and patient harm.




Disclosures:


Jonathan D. Hickman, DO¹, Melissa Lee, DO², Brett Sadowski, MD². C0071 - Mind the Gap: A Case of Autoimmune Pancreatitis, ACG 2022 Annual Scientific Meeting Abstracts. Charlotte, NC: American College of Gastroenterology.