IgG4-related thyroid disease

IgG4-related thyroid disease (IgG4-RTD) is a fibro-inflammatory condition of the thyroid gland that falls within the broader spectrum of IgG4-related disease (IgG4-RD), a systemic immune-mediated condition characterized by tissue infiltration with IgG4-positive plasma cells and varying degrees of fibrosis. IgG4-RTD encompasses two main thyroid manifestations: a fibrosing variant of Hashimoto thyroiditis (also known as IgG4-related thyroiditis or IgG4 thyroiditis) and Riedel thyroiditis, a rare condition involving dense fibrosis that extends beyond the thyroid capsule into surrounding cervical tissues. Both conditions are classified under ICD-10 code E06.5. Patients with IgG4-related thyroiditis typically present with a firm, diffusely enlarged thyroid gland (goiter), often accompanied by hypothyroidism. Riedel thyroiditis presents as a hard, fixed thyroid mass that may cause compressive symptoms including dysphagia (difficulty swallowing), dyspnea (difficulty breathing), and hoarseness due to involvement of surrounding structures such as the trachea, esophagus, and recurrent laryngeal nerve. Elevated serum IgG4 levels are frequently observed, and biopsy reveals characteristic dense lymphoplasmacytic infiltration with abundant IgG4-positive plasma cells and storiform fibrosis. Other organs may be simultaneously or sequentially affected, including the pancreas, salivary glands, retroperitoneum, and lungs. Treatment depends on the severity and extent of disease. Glucocorticoids (such as prednisone) are the first-line therapy and often produce significant clinical improvement, particularly in the inflammatory phase. For steroid-refractory or relapsing cases, immunosuppressive agents such as mycophenolate mofetil, azathioprine, or rituximab (an anti-CD20 monoclonal antibody) may be employed. Surgical intervention may be necessary in cases of Riedel thyroiditis with significant airway or esophageal compression. Thyroid hormone replacement therapy is required for patients who develop hypothyroidism. Long-term follow-up is important as the disease may relapse and other organ involvement may develop over time.

Common questions about IgG4-related thyroid disease