Subacute thyroiditis presenting with creeping in a 6-year-old boy.

Among the types of acute thyroiditis, subacute thyroiditis (SAT) is rare in children, and there is limited knowledge regarding its characteristics in pediatric cases. We present a case of SAT in a 6-yr-old boy who was brought to our hospital with high fever and pain in the front portion of the neck. Acute suppurative thyroiditis (AST), which is common in children, was suspected initially. Tenderness observed in the thyroid corresponded to a hypoechoic region on ultrasonography. The tenderness subsequently shifted to the isthmus, which was evident as a hypoechoic region on ultrasonography. Movement of hypoechoicity is typical of creeping thyroiditis, wherein the pain and tenderness can be unilateral or may start on one side and subsequently shift to the contralateral side after days or even weeks. Based on this characteristic and changes in laboratory parameters, the patient was diagnosed as a case of creeping thyroiditis. Improvement was observed in the patient without the use of anti-inflammatory drugs. At the 2-yr follow-up, the patient did not have thyrotoxicosis or relapse. Although AST is more prevalent than SAT in children, ultrasonography findings of creeping thyroiditis may be an important indicator for the diagnosis of SAT in pediatric patients.