S1284 Novel Molecular Immune System Imaging of Autoimmune Pancreatitis with L-FAC-PET Imaging: Comparison with FDG-PET

Abstract

Background & Aims: Autoimmune pancreatitis (AIP), a rare but treatable form of pancreatitis, is now recognized as a part of IgG4-related systemic disease characterized by elevated serum IgG4 levels, multi-organ IgG4-rich lymphoplasmacytic infiltration and an almost universal response to steroids. Detailed evaluation and management of AIP in the USA has been reported only from one center. Our aim was to systematically review the clinical presentations, evaluation and management of AIP at a large tertiary center. Methods: Using search terms “autoimmune pancreatitis”, “pancreatic pseudotumor”, “lymphoplasmacytic sclerosing pancreatitis” and “idiopathic rapidly progressive cholangitis”, we identified 29 AIP patients treated at the Digestive Disorders Center of the University of Pittsburgh Medical center from 1998-2007. Three patients with cancers (2 pancreatic and 1 gastric) diagnosed concurrently or within a short period of diagnosis were excluded. Patient records were reviewed to obtain information on demographics, clinical presentation, laboratory and imaging findings, extrapancreatic involvement, treatment response and recurrence. Results: Median age at presentation was 62.5 years (range 23-86), 65% were males, and 88% were Caucasian. The most common presentation included new onset mild abdominal pain (65 %), jaundice (62%), weight loss (42%) and diabetes (23%). Pancreatic mass, enlargement or prominence on imaging was present in 85% patients. An elevation of serum IgG4 to >140 mg/dl and >280 mg/dl was seen in 8 (44.4 %) and 5 (27.8%) of the 18 patients respectively in whom it was measured. The most common extrapancreatic finding was extrapancreatic/intrahepatic biliary strictures (35%). Peri-pancreatic vascular complications were noted in 23% patients. Six patients underwent partial or complete pancreatectomy. Partial/complete response to initial steroid treatment was seen in 19/19 patients. Recurrences were common, especially in patients with proximal biliary strictures, and usually responded to a combination of steroids and azathioprine. Any one of the commonly used diagnostic criteria (HISOR-t, Japanese, Korean) was fulfilled in 85% cases. Conclusions: In this second major US series, we confirm several findings previously reported on AIP. Serum IgG4 elevation was less prevalent in our series compared to previous reports.We highlight presence of clinically significant vascular complications in a subset of AIP patients. In patients with proximal biliary strictures consideration should be given to starting an immunosuppressive agent with the initial steroid therapy. The current diagnostic criteria may not identify all AIP patients.