History and Physical Examination
Riedel thyroiditis (RT) is characterized by the replacement of normal thyroid parenchyma with dense fibrotic tissue and by the extension of this fibrosis to adjacent structures of the neck. Most patients are euthyroid, but hypothyroidism is noted in approximately 30% of cases. Rarely, hyperthyroidism can occur, but this is probably secondary to a coexisting condition.
Clinical features of RT closely resemble those of anaplastic carcinoma of the thyroid. Patients note a nonpainful, rapidly growing thyroid mass.
Patients typically present with a hard, fixed, painless goiter. The character of the thyroid gland is often described as stony or woody. The onset of the goiter may be sudden, but it is usually gradual.
Local compressive symptoms are frequent and can include the following:
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Neck tightness or pressure
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Dyspnea
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Dysphagia
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Hoarseness
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Choking
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Cough
Such symptoms are the result of the increasing thyroid mass or are due to the extension of the fibrotic process to adjacent neck structures (eg, strap muscles, trachea, esophagus, recurrent laryngeal nerve).
Hypoparathyroidism is rare and presumably reflects fibrotic involvement of the parathyroid glands. Recurrent laryngeal nerve paralysis is also uncommon, but it can be observed in extensive disease. [11]
Approximately one third of patients with RT have an associated extracervical manifestation of multifocal fibrosclerosis. These manifestations can include the following [8] :
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Retroperitoneal fibrosis
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Mediastinal fibrosis
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Orbital pseudotumor
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Pulmonary fibrosis
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Sclerosing cholangitis
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Lacrimal gland fibrosis
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Fibrosing parotitis
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Gross pathology of Riedel thyroiditis. The cut edge is avascular, with a characteristic white color. Image courtesy of SL Lee.
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Riedel thyroiditis. The atrophic thyroid follicles are surrounded by a dense, inflammatory infiltrate composed of lymphocytes, plasma cells, and eosinophils and accompanied by dense fibrosis. The wide bands of keloid-type collagen located between the individual follicles and surrounding clusters are a common feature of this condition.
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Riedel thyroiditis. This vein shows infiltration of its wall by a heavy, inflammatory infiltrate.
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Riedel thyroiditis. The inflammatory infiltrate and dense, pink bands of fibrosis can obliterate thyroid follicles. Image courtesy of SL Lee.
