IgG4-Mediated Sclerosing Riedel Thyroiditis: A Multidisciplinary Case Study and Literature Review

Area of Science:

• Endocrinology
• Immunology
• Pathology

Background:

• Riedel thyroiditis (RT) is a rare, chronic inflammatory condition affecting the thyroid.
• It involves extensive fibrosis that can extend beyond the thyroid gland.
• RT can be associated with IgG4-related disease.

Purpose of the Study:

• To present a case of Riedel thyroiditis with unusual presentation and diagnostic challenges.
• To discuss the histopathological and immunohistochemical findings.
• To review the literature and explore the immunopathogenesis of RT in the context of IgG4-related disease.

Main Methods:

• Case presentation of a 52-year-old female with initial subacute thyroiditis symptoms.
• Fine-needle aspiration cytology and subsequent thyroidectomy with histopathological examination.
• Immunohistochemistry for IgG4-secreting plasma cells and macrophage phenotyping (M2 subtype).
• Computed tomography (CT) scan for extrathyroidal involvement.
• Literature review.

Main Results:

• Histopathology revealed scleroatrophic thyroiditis with chronic inflammation, eosinophils, rare atrophic follicles, and obliterative vasculitis.
• Immunohistochemistry confirmed abundant IgG4-positive plasma cells and M2 macrophages.
• CT scan showed peritracheal fibrosis and subtle pulmonary changes.
• Diagnosis of Riedel thyroiditis was established, with potential links to IgG4-related disease.

Conclusions:

• Riedel thyroiditis presents a diagnostic challenge, often requiring surgical intervention for definitive diagnosis.
• The findings support the association between RT and IgG4-related disease, highlighting shared immunoinflammatory mechanisms.
• Understanding these mechanisms is crucial for managing this rare condition.