This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thyroiditis, Subject name: Pathology
[{'content': 'IgG4-related disease is a newly recognized entity. Which of the following thyroid abnormality is associated with this condition? \nSelect and explain. \nA. De quervain thyroiditis, B. Postpaum thyroiditis, C. Reidel thyroiditis, D. Hashimoto thyroiditis', 'role': 'user'}, {'content': 'Answer: C \nExplanation: - Riedel thyroiditis, a rare disorder associated with IgG4 characterized by extensive fibrosis involving thyroid & contiguous neck structures. - The presence of a hard & fixed thyroid mass clinically simulates a thyroid carcinoma; but unlike thyroid carcinoma it is seen in young pts. - It may be associated with fibrosis in other sites like trachea, esophagus etc resulting in stridor, dysphagia etc. - Treated by rituximab/ tomoxifen/ steroids. EXTRA EDGE: - IgG4-Related diseases are: Mikulicz syndrome (enlargement and fibrosis of salivary & lacrimal glands) Riedel thyroiditis idiopathic retroperitoneal fibrosis autoimmune pancreatitis, and inflammatory pseudotumors of orbit, lungs & kidneys.', 'role': 'assistant'}]