Prevalence, Diagnosis, and Profile of Autoimmune Pancreatitis Presenting with Features of Acute or Chronic Pancreatitis

Background & Aims: Little is known about how many patients with features of acute pancreatitis (AP) or chronic pancreatitis (CP) have autoimmune pancreatitis (AIP); most information comes from case reports. We explored the clinical profiles and relationship between these diseases. Methods: We evaluated 178 patients presenting to our Pancreas Clinic between January 2005 and June 2006 for evaluation of the etiology of their suspected pancreatitis; AIP was diagnosed when patients met HISORt (Histology, Imaging features, Serology, Other organ involvement and Response to steroid treatment) criteria. In a separate cohort of patients with AIP from our database, we identified patients who presented with features of AP (≥2 of abdominal pain, increased pancreatic enzymes, pancreatic inflammation determined by imaging analyses) or CP (≥1 of pancreatic calcification, irregular main pancreatic duct dilation, or marked atrophy) and determined their clinical profile. Results: Only 7/178 (3.9%) patients evaluated for etiology of suspected pancreatitis had AIP. Among 63 AIP patients in our database, 22 (34.9%) had features of AP (n = 15) or CP (n = 7) at presentation (average age 53.4 ± 19.0 years, all males). Patients with AIP and pancreatitis were characterized by presence of obstructive jaundice (59.1%), increased levels of liver enzymes (81.8%), increased levels of serum immunoglobulin G4 (80.9%), and other organ involvement (69.1%). All 19 patients presenting with pancreatitis who were treated with steroids responded to treatment. Conclusions: While AIP is an uncommon etiology for acute or chronic pancreatitis, >33% of AIP have features of acute or chronic pancreatitis at presentation.