[The different forms of IgG4-related disease].

Immunoglobulin G4-related disease (IgG4-RD) is a newly recognised immune-mediated disease of unknown origin. IgG4-related disease predominantly affects the pancreas (autoimmune pancreatitis type 1), biliary tract (IgG4-associated cholangitis) and salivary glands. However, based on distinct histopathological findings, IgG4-RD has also been described in nearly every organ of the human body. Patient characteristics include elevated IgG4 serum levels, massive infiltration of lymphocytes - in particular IgG4-positive B and plasma cells - in affected tissues and a good response to immunosuppressive treatment. If left untreated, the chronic inflammation associated with IgG4-RD may lead to fibrosis and organ failure. Here, we discuss diagnostic challenges in two patients who were ultimately diagnosed with IgG4-RD. Additionally, we make suggestions on when to consider a possible diagnosis of IgG4-RD and how to approach the patient, thus enabling early diagnosis and treatment.