A rare case of Riedel's thyroiditis: Immunoglobulin G4-related thyroid disease
Authors: Özer Özge , Yorulmaz Göknur , Badak Bartu , Tekin Emel 
Published: January 2023

Abstract

Introduction
Riedel's thyroiditis is a rare thyroiditis in which normal thyroid tissue is replaced by dense fibrous connective tissue. Its etiology is not fully known. An autoimmune process is thought to exist. In this disease group, lymphoplasmocytic tissue infiltration, mostly consisting of IgG4 (+) plasma cells and small lymphocytes, is seen accompanying fibrosis. In our case, we presented a very rare case of Reidel's thyroiditis.

Clinical Case
We report the case of a 46-year-old woman who came to the general surgery department with an enlargement at the base of her neck. Among the patient's complaints were dysphonia, a feeling of pressure and pain in the neck. She had no history of thyroid disease. Laboratory findings; TSH 0.06 uIU/ml (0.27–4.2), fT3 2.69 pg/mL (2.3–4.5), fT4 1.81 ng/dl (0.93–1.70), crp 73.6 mg/l (0.0–5.0), sedimentation 90 mm/h (0–20), leukocytes 11.74 10^3/ul (4.49–12.68), absolute neutrophil count 9.22 10 ^3/ul (1.9–7.9). Trucut biopsy was performed with the preliminary diagnosis of malignancy due to the history of a mass growing in a short time on the neck of the patient. Pathology result; “Intense fibrosis increase, severe lymphoplasmacytic cell infiltration rich in IgG4 positive cells. Thyroid follicle epithelial cells with ck7, panck, pax8, thyroglobulin, ttf1 positive and cea, ck20, alk negative Intense plasma cells with CD38 have polyclonal staining with kappa and lambda, and IgG4/IgG ratio &gt; 50%. In the background, cd3, pax5 and bcl2 and T cell-rich reactive inflammatory cells are accompanied. Obliterative vascular structures were noted in rust and elastic histochemical stains, and storiform fibrosis was observed in places on the ground. When histopathological and immunohistochemical findings are evaluated together, it is primarily compatible with IgG4-related disease/reidel thyroiditis.'' She was then referred to the endocrinology department. The serum IgG4 level was found to be above normal. She was started on steroid treatment with 64 mg daily methylprednisolone. A weekly control plan was made. In these controls, the steroid dose was gradually reduced. In the follow-up one week later, it was observed that the patient's CRP and sedimentation returned to normal values. There was also a decrease in enlargement in the neck area. In the third month of the treatment, the patient didn't want to continue the treatment. She did not visit our clinic for the next 3 months. Then, she came for the control after three months without treatment. Biochemistry and thyroid function tests were normal. The swelling in the neck area of the patient was completely gone.

Conclusion
Reidel's thyroiditis is a very rare disease with publications on the basis of case reports in the literature. Therefore, there are no broad-spectrum clinical studies. Clarity on treatment approaches was also not provided. We also benefited from case reports while managing our patient's treatment. We believe that our case will contribute to the literature for the same purpose.