Autoimmune Pancreatitis (AIP)

Abstract

Despite vast amount of knowledge attained regarding the clinical, serological, radiological, and pathological characteristics of AIP, it remains an elusive diagnosis to make with significant repercussions to patients. This report illustrates two patients with this condition. Patient A: A 79 year-old male presented with painless jaundice. An ERCP was performed and a biliary stent was placed. A 1.2 cm mass adjacent to the common bile duct was seen on EUS. IgG, ANA, AMA, and ASMA were normal. A Whipple's procedure was performed and revealed no malignancy. He presented two years later with abdominal pain and multiple pseudocytsts and pancreatitis was seen on CT. The previous biopsy of the pancreas was reinterpreted as AIP. Prednisone was started, and the patient improved. Patient B: A 56-year old female presented with epigastric pain. Physical examination and ultrasound were unremarkable. Lipase and sedimentation rate were elevated. Imaging revealed pancreatic changes suspicious for malignancy. Excisional biopsy specimen was consistent with AIP. The patient opted for surveillance and remained asymptomatic for several months. She later presented with an exacerbation, was started on prednisone, and quickly improved. After Sarles' first description of AIP, similar pathologic findings were found in patients with other autoimmune disorders. Our cases demonstrate the all-too-often outcome of diagnosis established only after surgery. Prospectively evaluated diagnostic criteria for AIP do not exist. Serum IgG, specifically IgG4, and positive autoantibodies are suggestive of AIP. Imaging often reveals focal or diffuse parenchymal inflammation. ERCP often reveals irregular narrowing of the main pancreatic duct and absence of lateral branches. Neither imaging nor laboratory findings are specific. Histology demonstrates periductal lymphocytic infiltration and fibrosis. EUS-obtained biopsies provide adequate samples. Although our patients were not diagnosed with AIP prior to surgery, post-surgical review of the specimens supported a later diagnosis of AIP and allowed for proper treatment and follow-up. • AIP remains an elusive diagnosis. • Patients who have been diagnosed with idiopathic pancreatitis after surgery may benefit from review of their pathology specimens to exclude AIP. • As our ability to diagnose AIP improves, more patients will avert unnecessary surgery.