<unk>  was first described by Semple, in 1864 and Bolby in 1888.<unk>  was reported to the International Congress of Surgery by Bernhard<unk>  in 1894 and 1896. It was initially considered to be the fibrous variant of Hashimoto's thyroiditis but was later recognized as a separate disease. The exact pathogenesis of<unk>  is not fully understood. The presence of thyroid autoantibodies and lymphoid infiltration of the thyroid gland resembling that of Hashimoto's thyroiditis might indicate an autoimmune etiology. It is considered that the infiltrating lymphocytes release cytokines which are responsible for the activation of fibroblasts responsible for the fibrosis.<unk>  is characterized by a replacement of the normal thyroid parenchyma by a dense fibrosis that invades adjacent structures of the neck and extends beyond the thyroid capsule. This makes the thyroid gland stone-hard and fixed to adjacent structures. A shared mechanism with retroperitoneal fibrosis and sclerosing cholangitis has been suggested.<unk>  is considered to have autoimmune etiology and may be caused by the eosinophilia and the proliferation fibroblast as a result of cytokines released by inflammatory cells.<unk>  must be differentiated from other causes of thyroiditis, such as De Quervain's thyroiditis, Hashimoto's thyroiditis, and suppurative thyroiditis.<unk>  is a rare disease with an approximate incidence of 1.06 cases per 100,000 individuals worldwide.<unk>  commonly affects individuals between 30-50 years of age. Females are more commonly affected by<unk> . Common risk factors in the development of<unk>  include genetic factors, medications such as lysergic acid, ergotamine, serotonin, and other autoimmune diseases such as Graves’ disease and Hashimoto's thyroiditis. If left untreated, patients with<unk>  may progress to develop complications such as painless neck pressure, hoarseness, stridor, dysphagia, hypothyroidism, hypoparathyroidism, Horner's syndrome, and occlusive phlebitis. Prognosis is generally good and the disease-specific death rate ranges from 6 to 10%. Diagnostic criteria of<unk>  is based on the histopathological findings and includes infiltration of inflammatory cells in the thyroid gland, extension beyond the capsule, evidence of occlusive phlebitis and absence of giant cells, lymphoid follicles, or granulomas. The hallmark of<unk>  is hard and fixed thyroid mass. A positive history of other autoimmune diseases and the use of certain medications is suggestive of<unk> . The most common symptoms of<unk>  include hard and fixed neck mass, painless goiter, dysphagia, dyspnea, and hoarseness. Less common symptoms of<unk>  include muscular cramps, paresthesias, fatigue, and dry skin. Patients may have the clinical signs of hypocalcemia such as positive Chvostek sign and positive Trousseau sign. Laboratory findings consistent with the diagnosis of<unk>  include elevated ESR, mild elevation of thyroid peroxidase antibodies and occasionally elevated TSH levels. X-ray is helpful to identify esophageal or tracheal compression. CT scan findings suggestive of<unk>  include hypodense infiltrative mass, invasion of nearby soft tissues, compression of the trachea, and esophageal compression. MRI findings suggestive of<unk>  include focal, homogeneous hypointensity in T1 and T2. Ultrasound findings suggestive of<unk>  include hypoechogenicity, thyroid nodule infiltrating adjacent structures, and absence of blood flow on Doppler ultrasound. 24-hour iodine-123 uptake is absent or decreased in<unk> . Other diagnostic studies for<unk>  include pathological analysis, which demonstrates inflammatory cells infiltration, fibrosis with hyalinization, and extension of fibrosis outside the capsule, and immunohistochemical analysis, which demonstrates the predominance of T lymphocytes, strong positive stain to thyroglobulin, the presence of CD8+, CD4+ and plasma cells. Pharmacologic medical therapies for<unk>  include corticosteroids, tamoxifen, and mycophenolate mofetil. Surgery is usually reserved for patients with esophageal or tracheal compressive symptoms.
Riedel's thyroiditis
De Quervain's thyroiditis
Hashimoto's thyroiditis
Silent thyroiditis
Postpartum thyroiditis
Graves' disease
Follicular thyroid cancer
Primary thyroid lymphoma