title: A small subgroup of Hashimoto's thyroiditis is associated with IgG4-related disease.
abstract: IgG4-related disease is a newly identified syndrome characterized by high serum IgG4 levels and increased IgG4-positive plasma cells in involved organs. The incidence of IgG4-related thyroiditis in the Caucasian population of Europe is unknown. We investigated formalin-fixed thyroid gland samples of 216 patients (191 Hashimoto's thyroiditis, 5 Riedel's thyroiditis, and 20 goiters, as controls), morphologically, and immunohistochemically. Cases were divided into two groups: IgG4-related Hashimoto's thyroiditis (24 cases) together with Riedel thyroiditis (1 case) and 171 non-IgG4-related thyroiditis. Compared to the non-IgG4-related cases, IgG4-related thyroiditis showed a higher IgG4/IgG ratio (0.6 vs. 0.1, p < 0.0001), a higher median IgG4 count (45.2 vs. 6.2, p < 0.0001), an association with younger age (42.1 vs. 48.1 years, p = 0.036), and a lower female-to-male ratio (11:1 vs. 17.5:1). Fibrous variant of Hashimoto's thyroiditis was diagnosed in 23 of the 24 IgG4-related cases (96 %) and in 13 of 167 (18 %, p > 0.001) non-IgG4-related cases. The single case of IgG4-related Riedel's thyroiditis also showed a higher median IgG4 plasma cell count (56.3 vs. 14.3) and a higher IgG4/IgG ratio (0.5 vs. 0.2) than the four cases of non-IgG4-related Riedel's thyroiditis. Our data suggests the incidence of IgG4-related disease (IgG4-RD) of the thyroid gland in Europe is considerably lower than that observed in other studies. A significant elevation of IgG4-positive plasma cells was only found in a small group of Hashimoto's thyroiditis and then accompanied by intense fibrosis, indicating an association with IgG4-RD. Morphologically, IgG4-RD of the thyroid gland differs from that in other organ systems, exhibiting a dense fibrosis without intense eosinophilia or obliterative phlebitis.
authors.affiliation: Institute of Pathology, Staedtisches Klinikum Munich, Sanatoriumsplatz 2, 81545, Munich, Germany.|Institute of Pathology, Technical University Munich, Munich, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Jokisch
authors.affiliation: Institute of Pathology, Staedtisches Klinikum Munich, Sanatoriumsplatz 2, 81545, Munich, Germany.|Institute of Pathology, University of Wuerzburg, Wuerzburg, Germany.
authors.forename: Irene
authors.initials: I
authors.lastname: Kleinlein
authors.affiliation: Institute of Medical Statistics, Technical University Munich, Munich, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Haller
authors.affiliation: Institute of Pathology, Staedtisches Klinikum Munich, Sanatoriumsplatz 2, 81545, Munich, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Seehaus
authors.affiliation: Department of Surgery, Krankenhaus Martha-Maria, Munich, Germany.
authors.forename: Heinrich
authors.initials: H
authors.lastname: Fuerst
authors.affiliation: Institute of Pathology, Staedtisches Klinikum Munich, Sanatoriumsplatz 2, 81545, Munich, Germany. marcus.kremer@tum.de.|Institute of Pathology, Technical University Munich, Munich, Germany. marcus.kremer@tum.de.
authors.forename: Marcus
authors.initials: M
authors.lastname: Kremer
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001327:Autoimmune Diseases / Q000276:immunology*; D005260:Female; D005355:Fibrosis / Q000276:immunology / Q000473:pathology*; D006042:Goiter / Q000473:pathology; D050031:Hashimoto Disease / Q000150:complications / Q000276:immunology / Q000473:pathology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D008297:Male; D008875:Middle Aged; D010950:Plasma Cells / Q000166:cytology* / Q000276:immunology
chemical_list: D007074:Immunoglobulin G
keywords: Autoimmune thyroiditis; Fibrosing variant of Hashimoto’s thyroiditis; IgG4-related disease; Riedel’s thyroiditis