Hyperthyroidism resembling subacute thyroiditis following the penetration of the thyroid gland by a fish bone: A case report and review of the literature

Background: Penetration of the thyroid gland by a fish bone is rare, and there is no literature describing a patient with hyperthyroidism at initial examination in whom the thyroid gland was penetrated by a fish bone.Case presentation: A 51-year-old woman visited our hospital with left-sided neck pain. She had sensed a foreign body in her throat when eating a fish the previous day, but no abnormality was found by endoscopy. Blood examination revealed hyperthyroidism, and ultrasonography (US) revealed enlargement of the bilateral lobe with multiple adenomatous nodules and heterogeneous hypoechoic areas. The presumptive diagnosis was subacute thyroiditis, and treatment with prednisolone was initiated. Pain was reduced and tenderness moved to the right lobe. The phenomenon was diagnosed as creeping thyroiditis. However, computed tomography (CT) on day 4 demonstrated a linear hyperdense body in the left lobe. Esophagogastroduodenoscopy was repeated and revealed a fissure at the cervical esophagus. Her condition was then diagnosed as penetration of a fish bone into the thyroid gland. She was treated conservatively with monitoring to observe the course. Inflammatory signs significantly improved, so she was discharged on day 15. Subsequent CT and US did not show the presence of the fish bone. Conclusions: Penetration of the thyroid gland by a fish bone could result in a clinical course resembling subacute thyroiditis. CT and careful endoscopic inspection should be performed for patients with hyperthyroidism if foreign body insertion is not ruled out from the medical history.