<prompt> A young patient has a midline, tender swelling in neck occurring after an attack of sore throat. The diagnosis is -Acute thyroiditisThyroglossal cystSub acute thyroiditisToxic goiter  <response>: Diagnosis in this case is subacute thyroiditis. Symptoms are more severe in acute thyroiditis with complications and acute thyroiditis is more common in children.Just take a look of acute thyroiditis. Acute thyroiditis is rare and due to suppurative infection of the thyroid. More common in children and often is preceded by an upper respiratory tract infection or otitis media.EtiologyThe thyroid gland is inherently resistant to infection due to its extensive blood and lymphatic supply, high iodide content, and fibrous capsule.Infectious Agents can Seed Thyroid1. Via hematogenous or lymphatic route2. Via direct spread from persistent pyriform sinus fistulae or thyroglossal duct cysts3. As a result of penetrating trauma4. Due to immunosuppression Streptococcus and anaerobes account for about 70 of cases. In children and young adults, MC cause is presence of a pyriform sinus remnant of the fourth branchial pouch that connects the oropharynx with thyroid, such sinuses are predominantly left-sided. Long-standing goiter and degeneration in thyroid malignancy are risk factors in elderly.Clinical Features Thyroid pain, often referred to the throat or ears, and a small, tender goiter. Fever, dysphagia and erythema over the thyroid. Systemic symptoms of a febrile illness and lymphadenopathy. Complications such as systemic sepsis, tracheal or esophageal rupture, jugular vein thrombosis, laryngeal chondritis, and perichondritis or sympathetic trunk paralysis may also occur.Diagnosis ESR and WBC count are usually increased, but thyroid function is normal. FNA biopsy shows infiltration by polymorphonuclear leukocytes. Culture of the sample can identify the organism. Persistent pyriform sinus fistula should be suspected in children with recurrent acute thyroiditis. A barium swallow demonstrates the anomalous tract with 80 sensitivity.Treatment Parenteral antibiotics and drainage of abscesses. Patients with pyriform sinus fistulae require complete resection of the sinus tract, including the area of the thyroid where the tract terminates, to prevent recurrence. 