Abstract

Riedel's thyroiditis is a rare chronic inflammatory disease of the thyroid characterised by dense fibrosis that replaces normal thyroid parenchyma. The etiology is unknown. As per one school of thought it is believed that it is an autoimmune disease while another view is that it is a primary fibrotic disorder. Because of its hard consistency and fixation to adjacent structures it can mimic a thyroid malignancy. Local compressive symptoms, dysphagia, dyspnoea, and hoarseness of voice are the common presenting features. Patients do well with corticosteroid therapy.

Introduction

Riedel Thyroiditis is a rare chronic inflammatory disease of the thyroid gland characterized by dense fibrosis that replaces normal thyroid parenchyma. It was first recognised in 1883 by Professor Bernhard Riedel. He used the term ‘eisenharte struma’ to describe the stony hard consistency of the thyroid gland.1 The etiology of Riedel Thyroiditis (RT) unknown. One school of thought is that it is an autoimmune disease while another view is that it is a primary fibrotic disorder.2,3 We encountered one such case of RT in a 42-year-old lady who presented with hoarseness of voice since six months. The patient was euthyroid and had right vocal cord palsy.

Case Report

Our patient, a 42-year-old, presented with hoarseness of voice of 6 months duration. She also had right vocal cord palsy. On account of an enlarged prelaryngeal lymph node clinicians suspected carcinoma thyroid. A right hemithyroidectomy was performed. the hemithyroidectomy specimen received in our department measured 4 x 2.5 x 1 cm.

External surface was congested. Cut surface showed (Fig. 1) single white nodule 0.2 x 0.1 cm at one pole of the thyroid (arrow). A firm fibrous whitish area measuring 2 x 0.5 cm (arrow head) was seen a little away from the nodule.

Rest of the thyroid was unremarkable.

Multiple histology sections studied showed (Fig. 2) extensive replacement of the thyroid parenchyma with dense keloid like fibrosis, intermixed with well - developed lymphoid follicles and scattered lymphocytes and plasma cells. The fibrotic process extended beyond the thyroid capsule with involvement of the perithyroid soft tissues and skeletal muscle, consistent with Riedel's disease.

Discussion

Riedel's thyroiditis is an extremely rare form of chronic thyroiditis in which the thyroid gland is replaced by a fibroinflammatory process which partially destroys the thyroid. Patients more commonly are around 30-60 years of age (Avg. age 48 years).1,4 A marked female preponderance has been noted. Most of the patients are euthyroid at the time of presentation. The etiology of this condition is unknown. One view is that it is an autoimmune disease due to the good effect of the steroid treatment, frequent presence of thyroid antibodies, lymphoid infiltration of the thyroid gland and at times focal vasculitis.

Fig. 1 : Cut surface showing a single white nodule 0.2 x 0.1 cm at one pole of the thyroid (arrow). A firm fibrous whitish area measuring 2 x 0.5 cm (arrow head) was seen a little away from the nodule.	Fig. 2 : Histology showing extensive replacement of the thyroid parenchyma with dense keloid like fibrosis, intermixed with well - developed lymphoid follicles and scattered lymphocytes and plasma cells and the fibrotic process extending beyond the thyroid capsule (100 X). Inset to highlight extensive fibrosis and lymphoid follicles (400 X).

However the presence of normal lymphocyte populations and normal serum complement levels weighs against an autoimmune mechanism.1 Another view is that it is a primary fibrotic disorder supported by its association with multifocal fibrosclerosis.1 Because of the stony hard consistency of the thyroid gland and its fixation to the adjacent structures, it can mimic a malignancy.6 Patients present with local compressive symptoms such as neck tightness or pressure, dyspnoea, dysphagia, hoarseness of voice and chocking. The thyroid lesion is non-painful and rapidly growing. Patients respond well to corticosteroid therapy.6

References

1. Guerin CK, Boone JL. Riedel thyroiditis. www.emedicine.com July 20, 2006.
2. Zimmermann BT, Feldt RU. Riedel thyroiditis : an autoimmune or primary fibrotic disease. J Intern Med 1994;253(3):271-74.
3. Malotte MJ, Chonkich GD, Zuppan CW. Riedel's thyroiditis. Arch Otolarygol Head Neck Surg 1991; 117 (2) : 214-17.
4. Papi G, Corrado S, Cesinaro AM, et al. Riedel's thyroiditis : Clinical, pathological and imaging features. Int J Clin Pract 2002; 56 (1) : 65-67.
5. Schwaegerie SM, Bauer TW, Esselstyn CB Jr. Riedel's thyroiditis. Am J Clin Pathol 1988; 90 (6) : 715-22.
6. Geissier B, Wagner T, Dorn R. Extensive sterile abscess in an invasive fibrous thyroiditis (Riedel's thyroiditis) caused by an occlusive vasculitis. J Endocrinol Invest 2001; 24 (2) : 111-15.

*Associate Professor; **Resident, Department of Pathology, LTMMC and LTMGH, Sion, Mumbai - 400 022.