Introduction: Autoimmune pancreatitis (AIP) is most commonly an IgG4-related disease (type 1 AIP). Type 2 AIP is rare, more common in younger adults, does not typically recur, and is associated with inflammatory bowel disease (IBD). There are no diagnostic serum tests for type 2 AIP and the gold standard is tissue pathology demonstrating neutrophilic infiltration in the pancreatic ducts.
Case Description/Methods: A 33 year old female presented with recurrent episodes of pancreatitis. She did not have a clear etiology for pancreatitis including no alcohol use, no gallstones or hepatobiliary abnormalities on repeated imaging, normal levels of triglycerides, calcium, and IgG4, and she was not on any offending medications. MRI pancreas had shown an area of abnormal diffusion and delayed relative increased enhancement in the pancreatic tail. Due to recurrent attacks of unclear etiology, she underwent a distal pancreatectomy with splenectomy. Pathology from the distal pancreas showed periductal lymphoplasmacytic inflammatory infiltrates with neutrophilic inflammation in the ductal epithelium and acinar atrophy in majority of large and medium sized pancreatic ducts, and a negative IgG4 stain. These changes were most consistent with type 2 AIP.
During this time, she started having bloody diarrhea and colonoscopy showed proctitis with the rest of the colon and terminal ileum appearing normal. Rectal biopsy showed chronic active proctitis. These symptoms improved with topical mesalamine.
Despite the pancreatectomy, she continued to have recurrent episodes of pancreatitis with lipase elevations to 300-800, and CT findings of peripancreatic stranding and interstitial edema. She could not tolerate prednisone (side effects of confusion and hallucinations) or azathioprine (developed chest and abdominal pain). In order to manage her abdominal pain, she underwent celiac plexus blocks with only minimal relief. Currently, she is undergoing screening for initiation mycophenolate mofetil or rituximab.
Discussion: Type 2 AIP is a rare and challenging diagnosis, requiring histological confirmation and a multidisciplinary team approach. There is a significant overlap with IBD, predominantly ulcerative colitis, prevalent in up to 15-30% of patients. Concomitant AIP and IBD does not appear to impact disease severity of the other. Relapse is not typical and treatment strategies commonly target both AIP and IBD including steroids, azathioprine, and TNF alpha inhibitors.
