<prompt> IgG4-related disease is a newly recognized entity. Which of the following thyroid abnormality is associated with this condition?De quervain thyroiditisPostpaum thyroiditisReidel thyroiditisHashimoto thyroiditis  <response>: - 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. 