How to diagnose IgG4-related disease

We read with great interest the editorial by Fox and Fox1 describing the use of serum immunoglobulin G4 (IgG4) concentrations as a marker for IgG4-related disease (IgG4-RD). IgG4-RD is a fascinating clinical entity including a wide variety of diseases, formerly diagnosed as Mikulicz’s disease, autoimmune pancreatitis (AIP), interstitial nephritis, prostatitis and retroperitoneal fibrosis.2 3 However, universal criteria for IgG4-RD have not yet been established at present, making its diagnosis in some patients ambiguous leading to many IgG4-RD mimickers.

A 3-year investigation by the Japanese IgG4 team, organised by the Ministry of Health, Labour and Welfare (MHLW) of Japan, has reached a consensus, in that IgG4-RD can occur in various organs, with clinical symptoms depending on lesion location. Characteristics common to all forms of IgG4-RD include elevated serum IgG4 concentration and tissue infiltration by IgG4-positive plasma cells, accompanied by tissue fibrosis and sclerosis.