IgG4-Related Hashimoto's Thyroiditis of the Thyroid Gland

Immunoglobulin (Ig) G4-related Hashimoto's thyroiditis is a newly discovered subtype of Hashimoto's thyroiditis and characterized by thyroid inflammation and marked fibrosis. IgG4-related Hashimoto's thyroiditis is very rare and there has been relatively little information available to date. A 46-year-old woman with a past history of thyroid dysfunction visited our outpatient clinic for severe anterior neck swelling. She complained of swallowing discomfort and pain due to severe goiter and was successfully treated with total thyroidectomy. Immunohistochemistry showed thyroid invasion by IgG4-positive cells and an IgG4/IgG ratio over 40%. The patient was diagnosed with IgG4-related Hashimoto's thyroiditis. We report a very rare case of IgG4-related Hashimoto's thyroiditis with severe goiter. A more comprehensive understanding of the IgG4-related Hashimoto's thyroiditis may help physicians to allow proper diagnosis and treatment of patients with severe goiter.