Case Presentation: 33 yo Caucasian female with a PMH of Graves’ thyrotoxicosis and recurrent acute pancreatitis was admitted for suspected pancreatitis. She presented with acute onset epigastric pain radiating to back. She denied any associated symptoms. Exam showed yellowish discoloration of skin and epigastric tenderness. Recent ultrasound was negative for cholelithiasis or gallbladder wall thickening but had 4x3x3 mm gallbladder wall polyp. She denied history of alcohol use. Her triglycerides were normal and medications were carefully reviewed to rule out drug-induced pancreatitis. Chemistry showed lipase 1036 mg/dL, TB 1.5 mg/dL, DB 0.6 mg/dL, and ALP 238 U/L. FBG was < 180 mg/dL. UDS including serum alcohol was normal. Autoimmune serology for ANA was positive. IgG total was 1036 mg/dL and smooth muscle IgG antibody was 22 units. She was found to have Graves’ thyrotoxicosis with free T4 7.34 ng/dL, TSH < 0.005 mµ/L, TPO > 900 IU/mL, thyroglobulin 764 IU/mL, and TSI > 40 IU/mL. Endoscopy showed gastritis with gastric erosions. Small bowel and gastric biopsy was negative for villous atrophy, inflammation, and intraepithelial lymphocytes. CT abdomen showed ‘sausage-shaped’ pancreas with featureless borders. She was started on prednisone 40 mg twice daily. Her epigastric pain resolved and lipase deceased to 635 mg/dL. She was discharged on maintenance dose of dexamethasone 2 mg twice daily without a definite diagnosis for underlying etiology of her acute pancreatitis. Three months later she presented to an outside community hospital with diffuse abdominal pain and bloody diarrhea for 2 weeks. Colonoscopy showed circumferential lesion involving the rectum. Histological evaluation confirmed ulcerative colitis. Her lipase was 217 mg/dL and repeat CT abdomen showed normal pancreas without diffuse enlargement or atypical architecture. On basis of clinical, laboratory, and imaging findings from current and previous admission, a definite diagnosis of type II autoimmune pancreatitis (AIP) was made.

Discussion: Our patient was diagnosed with type II AIP based on typical imaging of pancreas, involvement of other organs (ulcerative colitis), and response to steroids. As reported in literature, up to 5-6% with type II AIP have inflammatory bowel disease, as seen in our patient. Unlike type I AIP, patients with type II AIP have a younger age of onset and equal sex distribution. Mayo Clinic has proposed “HISTORt” diagnostic criteria which includes presence of one or more of the following: elevated serum Ig4, characteristic imaging, diagnostic histology, other organ involvement, and response to steroids. AIP presents as a focal mass and is difficult to distinguish from pancreatic cancer. Early diagnosis of this potentially treatable disease is vital as response to steroids is dramatic, and unnecessary surgical intervention can be avoided. This case illustrates emphasis should be placed to use collective features to diagnose AIP as there are variations in presentations, including AIP diagnosis in absence of elevated IgG, AIP in young females, and differences in imaging findings of pancreas in AIP. Atypical presentation should be considered while making diagnosis of AIP.

Conclusions: AIP is a rare disease and little is known about the diagnosis or underlying etiology, especially in type II AIP. The clinical response to corticosteroids is rapid in type II AIP, reassuring the clinicians that decision to start corticosteroids was appropriate. Follow up imaging studies will justify this decision.