Relapse patterns in IgG4-related disease

Immunoglobulin (Ig)G4-related disease (IgG4-RD) is a chronic inflammatory disorder characterised by elevated levels of serum IgG4 and swollen organs with fibrosis and infiltration by abundant IgG4-positive plasmacytes. 1 2 Glucocorticoid treatment is effective for achieving clinical remission in the short term, 3 but about 20%-30% of cases present with relapse after steroid doses are reduced. 4 Serial changes of serum IgG4 levels are often considered to reflect the disease activity in routine clinical practice, 5 but how disease relapse occurs is not well understood. ExG lesions consisted of two cases with retroperitoneal fibrosis (RF), and one case each of autoimmune pancreatitis (AIP), tubulointerstitial nephritis (TIN) and lung involvement.