Unusual Multiorgan Immunoglobulin G4 (IgG4) Inflammation: Autoimmune Pancreatitis, Mikulicz Syndrome, and IgG4 Mastitis.

Autoimmune pancreatitis (AIP) type 1 is commonly associated with simultaneous involvement of extrapancreatic organs. Sclerosing cholangitis, sialadenitis, retroperitoneal fibrosis, Sjögren syndrome, and other extrapancreatic lesions are often observed concurrently with AIP. High levels of immunoglobulin G4 (IgG4) in the blood serum and affected tissues are typical of this diagnostic entity. We describe a case report of a 58-year-old female with findings of AIP (according to Asian criteria), IgG4-positive mastitis, and histologically verified Mikulicz syndrome. The effect of corticoid therapy supported the diagnosis of AIP and simultaneously led to the eradication of recurrent mastitis. To the best of our knowledge, this is the first reported case of concurrent findings of AIP and IgG4 mastitis. Our case report supports the concept of systemic IgG4 syndrome with multisystem involvement. Timely diagnosis and appropriate therapy can be effective in a high percentage of patients.