Pediatric differentiated thyroid carcinoma leading to fatal lung fibrosis

This case highlights the potential severe complications associated with several courses of RAI therapy in young children suffering from extensive lung metastases and underscores the need for careful treatment planning and long-term monitoring. Given the risks of RAI therapy, particularly the risk of fatal lung fibrosis, it is crucial to tailor RAI therapy carefully, especially in young patients. Notably, thyroglobulin levels can decrease even after cessation of RAI therapy, indicating that levels immediately post-therapy are not necessarily representing the development of the response over the following months.