Serum Immunoglobulin G4 Level Is a Poor Predictor of Immunoglobulin G4–Related Disease

Immunoglobulin G4-related disease (IgG4-RD) is characterized by elevation in serum IgG4 levels, typical multiorgan involvement and dramatic response to steroid therapy. We determined the predictive value of an elevated serum IgG4 for the diagnosis of IgG4-RD. We also sought to identify novel conditions, which have characteristic features of IgG4-RD.We identified all Mayo Clinic Rochester patients with serum IgG4 levels measured between January...