AUTOIMMUNE PANCREATITIS: DIAGNOSIS USING HISTOLOGY, IMAGING, SEROLOGY, OTHER ORGAN INVOLVEMENT AND RESPONSE TO STEROIDS

Background/Aims: Autoimmune pancreatitis (AIP) is a diagnostic challenge. We propose new diagnostic criteria for AIP based on characteristic histology, imaging features, serology, other organ involvement and response to steroid therapy (HISORt criteria). Our aims were to describe the spectrum of clinical presentations of AIP and determine the utility of pancreatic core biopsy, serum IgG4 elevation and response to steroid therapy in the diagnosis of AIP. Methods: We reviewed medical records of 40 patients meeting HISORt criteria for definite AIP identified from a prospectively maintained database. Of these 31 had pancreatic histology (resection (n = 11), core biopsy (n = 20), 28 had serum IgG4 measurement and 27 received steroid therapy. Serum IgG4 levels were measured in an additional 126 patients without AIP, including 44 with pancreatic cancer. Results: Presentations at diagnosis of AIP included obstructive jaundice (19/40), pancreatic mass (9/40), sclerosing cholangitis (7/40), recurrent pancreatitis (3/40) and steatorrhea (1/40). Pancreatic core biopsies were diagnostic of AIP in 14/20 (70%) patients. Serum IgG4 was elevated in 22/28 (78%) patients with AIP and 4/44 (10%) with pancreatic cancer. Eighteen (45%) AIP patients had other organ involvement; 12 had sclerosing cholangitis. All 27 AIP patients treated with steroids showed resolution of biliary strictures/pancreatic masses. Re-imaging within 5 weeks after start of steroid therapy showed partial resolution in 8/11 (72%). Conclusions: HISORt criteria identify a wide spectrum of clinical presentations of AIP. Pancreatic core biopsy, serum IgG4 elevation, presence of other organ involvement and rapid response to steroid therapy can aid in the diagnosis of AIP. AIP associated sclerosing cholangitis resolves with steroid therapy.