Riedel’s Fibrosing Thyroiditis Associated with Elevated Serum IgG4 Levels

Immunoglobulin G4-related sclerosing disease (IgG4-SD), also referred to as IgG4-related disease, is a newly described disease characterized by an infiltration of IgG4+ plasma cells in the early stages of the affection of an organ. Well documented in the pancreas and then detected in other organs, only few cases of thyroid affection have been reported. In addition, no case of IgG4-SD of the thyroid associated with high serum IgG4 levels has ever been described. We report here the first case.