DefinitionSubacute thyroiditis involves swelling (inflammation) of the thyroid gland that usually follows an upper respiratory infection.Alternative NamesDe Quervain's thyroiditis; Subacute nonsuppurative thyroiditis; Giant cell thyroiditis; Subacute granulomatous thyroiditisCauses, incidence, and risk factorsSubacute thyroiditis is a rare condition. It is thought to be caused by a viral infection. The condition often occurs after a viral infection of the upper respiratory tract, such as mumps and influenza.Subacute thyroiditis occurs most often in middle-aged women with recent symptoms of a viral respiratory tract infection.SymptomsThe most obvious symptom of subacute thyroiditis is pain in the neck. Sometimes the pain can spread (radiate) to the jaw or ears. Painful enlargement of the th