IgG4-related Sclerosing Disease: The Great Mimicker

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Purpose: A 65-year-old woman was evaluated for recurrent painless jaundice. Prior investigations included an endoscopic retrograde cholangiopancreatogram (ERCP) that showed a stricture in the distal common bile duct (CBD) with a negative cytology for malignant cells. She underwent a laparotomy during which a pancreatic head mass was found and biopsies revealed no malignancy. A palliative cholecystojejunostomy with gastroenterostomy was performed. Postoperatively the jaundice improved but she remained with epigastric pain, persistent nausea, anorexia and a 20-lb weight loss. Two weeks later she developed recurrent jaundice and a second ERCP demonstrated a hilar stricture. A presumptive diagnosis of multicentric cholangiocarcinoma was made and she was referred to hospice care. She then presented to our institution for evaluation. Serum Immunoglobulin G4 (IgG4) levels were normal. She underwent an endoscopic ultrasound (EUS) that showed no evidence of a pancreatic head mass. However, the entire pancreas was diffusely inhomogeneous and abnormal. The parenchyma presented alternating hypoechogenic and hyperechogenic areas with strands and lobulations. The outer border of the gland was lobular and the main pancreatic duct was normal. Biopsies of the pancreas showed changes consistent with chronic pancreatitis, with loss of the acinar parenchyma and residual islets and ducts seen with fibrosis and infiltration composed of mononuclear cells. Immunostain for CD138 was performed and very high numbers of plasma cells were observed infiltrating the tissue. Immunostain for IgG4 demonstrated approximately 10-15 positive cells per high power field. These findings and the patient's clinical presentation were most consistent with autoimmune pancreatitis and IgG4-related sclerosing cholangitis. The patient was started on prednisone followed by azathioprine and experienced a rapid and sustained clinical and biochemical response for several years even after stopping immunosuppressive therapy. After treatment, repeat imaging studies were performed which showed dramatic improvement in the above mentioned abnormalities. Autoimmune pancreatitis and IgG4-related sclerosing cholangitis are manifestations of IgG4-related sclerosing disease. Elevated serum IgG4 levels suggest this diagnosis but many times remain normal. Therefore a strong clinical suspicion should prompt a biopsy of the affected tissue with immunostaining with anti-IgG4 antibody. The disease responds well to immunosuppressive therapy. In the setting of suspected malignant tumors, IgG4-related sclerosing disease should be considered in the differential diagnosis to avoid unnecessary surgery and unfavorable as well as incorrect prognosis.