RESUMEN
Acute thyroiditis is a rare disease because of the sufficient supply of blood vessels and lymphatics in thyroid tissue, the high concentration of iodide in the thyroid tissue and the nearly completely isolated structure of the thyroid gland from the surrounding tissue via its capsule. The most common route of infection is from a pyriform sinus fistula and then the inflammation spreads from the sinus to the perithyroidal space. Computed tomography (CT) and magnetic resonance imaging (MRI) can show a low echogenic mass encircling thyroid gland and swelling of the perithyroidal tissue in acute suppurative thyroiditis. We experienced a case of acute perithyroiditis with thyrotoxicosis that developed in a 13-year old boy and he was diagnosed by the CT findings. The patient had complained of a low graded fever and neck swelling. The laboratory diagnosis and clinical course was like that of subacute thyroiditis, but the CT finding showed a show low echogenic mass encircling the thyroid glands and swelling of the perithyroidal tissue. Therefore, we diagnosed this patient with acute perithyroiditis. After treatment with antibiotics, he displayed clinical improvement and was discharged.