Riedel Thyroiditis

Riedel thyroiditis is a rare condition that affects the thyroid gland, a butterfly-shaped organ in the neck that controls metabolism. It causes the thyroid tissue to become replaced by dense, fibrous scar tissue, making the gland hard and fixed in place. This scarring can lead to symptoms like a painless neck mass, difficulty swallowing, or breathing problems if the scar tissue compresses nearby structures. The condition involves the immune system attacking the thyroid, leading to chronic inflammation and fibrosis. Because the thyroid becomes stiff and less functional, it can also cause hypothyroidism, where the body lacks enough thyroid hormones. Overall, it is a serious disorder that affects the neck and hormone regulation.

Riedel thyroiditis is a rare form of chronic thyroiditis characterized by extensive fibrosis that replaces normal thyroid parenchyma and often extends beyond the gland into adjacent neck tissues. It is considered part of the spectrum of IgG4-related disease, involving an autoimmune-mediated fibroinflammatory process. The fibrosis leads to a hard, fixed thyroid mass that can cause compressive symptoms such as dysphagia, dyspnea, or hoarseness. Histologically, it shows dense collagen deposition with a mixed inflammatory infiltrate rich in plasma cells and fibroblasts. Unlike other thyroiditis forms, it rarely causes hyperthyroidism but often results in hypothyroidism due to gland destruction. The condition is clinically significant because it can mimic thyroid malignancy and cause airway obstruction.