Patient: Male, 70Final Diagnosis: IgG4 RDSymptoms: JaundiceMedication: —Clinical Procedure: —Specialty: Gastroenterology and HepatologyObjective:Rare diseaseBackground:Type 1 autoimmune pancreatitis (AIP), also known as lymphoplasmacytic sclerosing pancreatitis (LPSP), is a rare cause of chronic pancreatitis, characterized by a fibro-inflammatory process. However, patients with AIP may have a good response to corticosteroid therapy. We describe a Tunisian patient with AIP that was confirmed to be an IgG4-related disease (IgG4-RD).Case Report:We describe a case of a 70-year-old man who was admitted to hospital for obstructive jaundice and abdominal pain. Serum liver function tests were abnormal and upper abdominal computed tomography (CT) imaging showed diffuse pancreatic swelling and strictures of the main pancreatic duct without any focal lesion. Pancreatico-biliary magnetic resonance imaging (MRI) showed a thickened rim surrounding the pancreatic duct Serum IgG4 levels were elevated, resulting in a diagnosis of IgG4-related AIP. The patient showed a good clinical, biochemical, and radiological response following steroid therapy in combination with azathioprine.Conclusions:The diagnostic workup of IgG4-RD is complex and usually requires a combination of clinical examination, imaging, and serological analysis. As this case report has demonstrated, IgG4-RD should be considered in patients who present with pancreatitis or AIP, because of the favorable response to steroid therapy, particularly when treatment is initiated early.