Autoimmune pancreatitis (PAI) is a rare pathology and an entity to consider in the differential diagnosis of obstructive jaundice and pancreatic mass. It is a chronic inflammatory disease of the pancreas with established clinical, radiological, serological and histopathological characteristics. The treatment is based on the use of corticosteroids and usually has a good response, with complete resolution of clinical, analytical and radiological parameters. We present the case of a 62-year-old woman with abdominal pain in the right hypochondrium and epigastrium associated with low weight. Normal laboratory tests. Abdominal TEM: pancreas increased in volume diffusely with peripancreatic halo. EUS: extensive heterogeneous lesion involving the head and body, FNA is performed. AP: lympho-plasmocitary infiltrate. IgG4: 520 mg / dL. It is determined that it is a probable type I autoimmune pancreatitis and it is decided to perform a therapeutic trial with corticosteroids. Tomographic control is performed at 4 weeks with adequate response.