Case Presentation: A 37 year old male with a history of asthma presented with a three day history of acute onset left upper quadrant (LUQ) abdominal pain, worse after meals and associated with nausea. He had no history of cholelithiasis, alcohol abuse or trauma. Vital signs on admission were in normal range. Exam revealed LUQ abdominal tenderness. Initial labs showed lipase > 3 times the upper limit of normal, mildly elevated ALP, normal AST and ALT, mildly elevated triglycerides and undetectable alcohol levels. RUQ ultrasound was negative for cholelithiasis or common bile duct dilatation. CT showed mild acute distal pancreatitis. Supportive treatment with IV fluids and analgesia led to improvement of symptoms and decrease in lipase. Chart review revealed previous positivity of anti-smooth muscle antibody (Ab) 1:80 titer and negative IgG4 Ab. Repeat testing confirmed negative IgG4 Ab and anti-smooth muscle Ab 1:20 titer. As an outpatient, he reported persistent LUQ abdominal pain. MRCP revealed a focal abnormal signal in the pancreatic tail, subtle area of decreased enhancement at body/tail junction of pancreas and pancreatic divisum. An endoscopic ultrasound revealed no signs of biliary tract obstruction, sludge or cholelithiasis and diffusely hypoechoic and lobular pancreatic parenchyma, without nodules or cysts. Fine needle aspirate of the pancreas was not performed due to risk of potentiating pancreatitis and minimal risk of malignancy by imaging. A trial of steroids was not administered due to improvement of symptoms without intervention.
Discussion: Despite the many causes of pancreatitis, approximately 10-40% of cases are labeled idiopathic (1). Young patients with no clear etiology after initial work up should be screened for less common causes such as autoimmune pancreatitis (AP). There is no available data regarding the precise prevalence of AP in the US.Type 1 AP is more common in males above 50 years of age and is associated with elevated IgG4 Ab levels and IgG4 related systemic involvement (2). Type 2 AP lacks IgG4 Ab, affects a younger age group and does not commonly present with systemic features. Type 2 AP co-occurs with inflammatory bowel disease in approximately 30% of cases (3). Standard treatment of AP is oral corticosteroids, often with a dramatic therapeutic response. Multiple histological and serologic criteria such as HISORt criteria have allowed for improved diagnosis of Type 1 AP (3,4). However, due to the lack of serologic markers and systemic involvement, diagnosis of Type 2 AP is elusive. There is promise for novel antibodies such as anti-PBP (plasminogen binding protein), but it is too early for clinical implementation (5). This case likely represents Type 2 AP, and biopsy would have been confirmatory. As patient’s symptoms improved and risk of inducing pancreatitis was higher, etiology remained idiopathic. Corticosteroids are not recommended routinely and should be used in symptomatic cases only; however, they should not substitute for a thorough search of an etiology. On the contrary, early corticosteroids may likely reduce long term effects of chronic pancreatitis such as exocrine insufficiency, diabetes mellitus, necrosis, increased risk of malignancy and poor quality of life from recurrent symptoms (2).
Conclusions: Diagnosis of Autoimmune Pancreatitis remains a challenge, especially in Type 2 Autoimmune Pancreatitis given lack of histologic and serologic tools. Decision making for steroid therapy is individualized, and highly dependent on presence of symptoms.