A Case of Recurrent Thyrotoxicosis in a Thyroglossal Duct Cyst 18 Years Following Thyroid Surgery.

Graves' disease (GD) is an immune-mediated condition related to high thyroid-stimulating immunoglobulin levels. Here, we present a rare case of recurrent thyrotoxicosis that developed in a thyroglossal duct cyst (TGDC) and the residual thyroid tissue in a 46-year-old female following subtotal thyroidectomy. In 2005, she was diagnosed with GD causing thyrotoxicosis and treated with subtotal thyroidectomy. In 2022, she was seen at our clinic with a neck swelling gradually growing in size over the last 10 years. On examination, the mass was found to be moving with tongue protrusion. She was on thyroxin 100 mcg daily, and the dose was reduced gradually until she was maintained on no therapy for hypothyroidism and was still thyrotoxic. The combined clinical, laboratory thyroid scintigraphy and ultrasonographic features favored early developing recurrent Graves' disease in the thyroid residual and TGDC. She was started on carbimazole and was referred for surgery. Our case represents a rare occurrence of recurrent GD in the thyroid residual and TGDC.