title: Riedel's thyroiditis association with IgG4-related disease.
abstract: BACKGROUND
  IgG4-positive (+) plasma cells have been reported in both Riedel's thyroiditis (RT) and Hashimoto's thyroiditis (HT). These cells are the hallmark of IgG4-related disease (IgG4-RD).
  
  
  OBJECTIVE
  We sought to determine whether RT is part of IgG4-RD spectrum.
  
  
  METHODS
  This was a case-control study performed at a tertiary medical centre. We included RT cases from the period 1958 to 2008 that had sufficient paraffin-embedded tissue for IgG4 immunostaining. Controls were patients with HT, age and gender matched, with similar pathology criteria.
  
  
  METHODS
  The main outcome measures were the intensity of the IgG4 staining and the clinical and histological correlates with IgG4-RD.
  
  
  RESULTS
  Six pairs of RT and HT were analysed. The mean age was 44·7 years. In both groups, 5/6 cases had positive IgG4 staining. The mean number of IgG4 + cells/ HPF, normalized to the degree of inflammation, was 3·2 ± 3·0 SD (RT) vs 0·9 ± 0·7 (HT), P = 0·15, for fibrotic areas and 2·1 ± 2·3 SD vs 1·0 ± 0·8 (P = 0·39) for areas with lymphoid aggregates. We found the number of IgG4 +  cells in RT to be inversely correlated with the duration of disease (P = 0·046). Three RT cases had associated comorbidities from the IgG4-RD spectrum while none of the HT cases had such conditions.
  
  
  CONCLUSIONS
  Riedel's thyroiditis is a component of IgG4-RD with the density of the IgG4 +  lymphocytic infiltrate being time dependent. In this small study, we did not identify differences in IgG4 infiltration between RT and HT, minimizing the utility of this marker in RT diagnosis.
authors.affiliation: Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA.
authors.forename: Marius N
authors.initials: MN
authors.lastname: Stan
authors.affiliation: Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA.
authors.forename: Vikram
authors.initials: V
authors.lastname: Sonawane
authors.affiliation: Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Sebo
authors.affiliation: Department of Health Sciences Research, Division of Biostatistics, Mayo Clinic, Rochester, MN, USA.
authors.forename: Prabin
authors.initials: P
authors.lastname: Thapa
authors.affiliation: Department of Internal Medicine, Division of Endocrinology, Diabetes, Metabolism and Nutrition, Mayo Clinic, Rochester, MN, USA.
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Bahn
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D002465:Cell Movement; D015897:Comorbidity; D003937:Diagnosis, Differential; D005260:Female; D050031:Hashimoto Disease / Q000175:diagnosis / Q000473:pathology; D006801:Humans; D007074:Immunoglobulin G / Q000032:analysis*; D007150:Immunohistochemistry; D008214:Lymphocytes / Q000166:cytology; D008297:Male; D008875:Middle Aged; D010950:Plasma Cells / Q000276:immunology*; D013966:Thyroiditis / Q000145:classification / Q000175:diagnosis* / Q000473:pathology
chemical_list: D007074:Immunoglobulin G