IgG4-related disease is an autoimmune disease characterized by a collection of clinical findings. Multiple organs are typically involved such as salivary glands, pancreas, orbital disease, and retroperitoneal fibrosis. A 84 year old male presented with 1 month history of malaise, jaundice,dry mouth, abdominal pain and 10lb weight loss. Physical exam revealed dry mucous membranes, scleral icterus, jaundice, and proptosis. His blood work revealed elevated LFT with a cholestatic pattern, TBILI 10.9, ALP 1230, AST 537, ALT 320. MRCP showed dilation of the CBD with a severe distal CBD stenosis, diffuse dilation and irregularity in the intrahepatic biliary tree. The patient underwent an EUS which demonstrated pancreatic parenchymal changes including hyperechoic foci, hypoechoic areas, a dilated pancreatic duct and prominent side branches and a fine needle biopsy was performed. An ERCP was performed and plastic biliary stent was placed and brushings for cytology were obtained. The cholangiogram demonstrated diffuse irregularity and rarefaction of the intrahepatic ducts. Histology of pancreatic biopsy showed pancreatic parenchyma with storiform fibrosis without signs of malignancy. An immunostain for IgG4 revealed increased number of cells, supportive of the diagnosis of autoimmune pancreatitis. Serum IgG4 was elevated at 257 and CA 19-9 was 221. A repeat EUS/ERCP with FNB and cholangiogram and stent change to a fully covered metal stent was performed. The patient was diagnosed with IgG4-RD characterized by Type 1 Autoimmune Pancreatitis, IgG4-related sclerosing cholangitis, salivary gland disease, and orbital disease. The patient was prescribed prednisone and reported dramatic improvement in his symptoms. Follow up CT scan showed chronic pancreatitis, but no pancreaticobiliary malignancy and labs showed normal transaminases. Diagnosis of IgG4-RD should be considered in patients presenting with biliary stricture, especially in the setting of systemic symptoms involving salivary glands, physical findings including proptosis, and evidence of pancreatitis. Although this diagnosis may masquerade as a malignancy or primary sclerosing cholangitis, characteristic clinical features, radiographic and endoscopic images as well as histologic findings can confirm the diagnosis. Management of IgG4-RD is very effective with corticosteroid therapy. Endoscopic therapy is an important adjunct to medical therapy to treat dominant biliary strictures and relieve obstructive jaundice.1434_A.tif Figure 1: Hypoechoic irregular area in the head of the pancreas1434_B.tif Figure 2: Pancreatic parenchyma with fibrosis, focal storiform, atrophy, mixed chronic inflammation and reactive changes1434_C.tif Figure 3: Intrahepatic branches with diffuse irregularity and rarefaction of ducts