Thyroiditis

Abstract

Thyroiditis, or inflammation of the thyroid, encompasses a great variety of entities, such as acute thyroiditis, granulomatous (de Quervain) thyroiditis, fibrous (Riedel) thyroiditis, Hashimoto thyroiditis, and focal lymphocytic thyroiditis. These entities are associated with varying degrees and types of inflammation and different underlying causes. Patients with acute thyroiditis often have symptoms including a painful thyroid gland with acute inflammation, which usually is caused by an infection, often a systemic bacterial infection that involves the thyroid secondarily. Patients with de Quervain granulomatous thyroiditis also commonly are symptomatic and have a painful thyroid gland. The thyroid shows nonsuppurative, granulomatous thyroiditis that often is viral and related to a prior upper respiratory infection. Fibrous (Riedel) thyroiditis generally is painless and presents as an enlarged, hard thyroid replaced by fibrosis, which may cause compressive symptoms and be worrisome for malignancy as the fibrosis extends beyond the thyroid. Hashimoto thyroiditis (struma lymphomatosa) is an autoimmune disorder associated with antimicrosomal (antithyroid peroxidase) antibodies. The thyroid in Hashimoto thyroiditis may be diffusely involved or fibrotic and shows a marked lymphoid infiltrate with follicles with germinal centers and prominent Hurthle cells. The fibrous variant of Hashimoto thyroiditis may be difficult to separate from fibrous (Riedel) thyroiditis. Focal lymphocytic thyroiditis is quite common and likely an incidental finding in thyroids, often from women and elderly people, showing foci of lymphoid aggregates in the thyroid.