IgG4-related disease is a newly recognized entity. Which of the following thyroid abnormality is associated with this condition?
**Core Concept**
IgG4-related disease is a **fibroinflammatory condition** characterized by tumor-like swelling of affected organs, infiltration of IgG4-positive plasma cells, and variable degrees of fibrosis. It can affect multiple organs, including the pancreas, biliary tree, salivary glands, and lacrimal glands. The condition is also known as IgG4-related sclerosing disease.
**Why the Correct Answer is Right**
The correct answer is associated with **Riedel's thyroiditis**, a rare form of chronic thyroiditis characterized by a dense fibrotic process that invades the thyroid gland and adjacent structures. Riedel's thyroiditis has been linked to IgG4-related disease, with many cases showing increased numbers of IgG4-positive plasma cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Not specifically associated with IgG4-related disease.
**Option B:** Not a recognized form of thyroiditis linked to IgG4-related disease.
**Option C:** Although a form of thyroiditis, it is not typically associated with IgG4-related disease.
**Clinical Pearl / High-Yield Fact**
IgG4-related disease can present with a wide range of clinical manifestations, and diagnosis often requires a combination of clinical, radiological, and histopathological findings. Riedel's thyroiditis is a rare but important consideration in the differential diagnosis of thyroid abnormalities.
**Correct Answer:** D. Riedel's thyroiditis.