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Riedel's Thyroiditis

Riedel's chronic sclerosing thyroiditis is rare and occurs chiefly in middle-aged women. The etiology is unknown. Some cases are considered to be an advanced state of Hashimoto's disease, but there is also evidence that it is a separate disease entity. It is characterized by fibrosis of the thyroid gland and adjacent structures and may be associated with fibrosis elsewhere, especially in the retroperitoneal area. The presence of eosinophils has recently been demonstrated histologically, suggesting a unique autoimmune response to fibrous tissue.

Symptoms develop insidiously and are related chiefly to compression of adjacent structures, including the trachea, esophagus, and recurrent laryngeal nerves. Constitutional evidence of inflammation is uncommon. The thyroid gland is moderately enlarged, stony hard, and usually asymmetrical. The consistency of the gland and the invasion of adjacent structures suggest carcinoma, but there is no enlargement of regional lymph nodes. Temperature, pulse, and leukocyte count are normal. Hypothyroidism is unusual. The RAIU may be normal or low. Circulating thyroid autoantibodies are less frequent and are found in lower titers.

Surgery may be required to preserve tracheal function.

If extensive involvement of perithyroid tissues is present, resection of the isthmus may relieve some symptoms. Treatment with thyroid hormone relieves the hypothyroidism.