Case Report: Graves' disease in a toddler with maple syrup urine disease: therapeutic challenges and surgical resolution.

A two-and-a-half-year-old girl with a known diagnosis of Maple Syrup Urine Disease (MSUD) developed challenging Graves' disease while undergoing liver transplant workup for definitive MSUD management. Initial low-dose methimazole failed to control hyperthyroidism; gradual dose escalation resulted in better control; however, the patient developed hepatotoxicity. Dose reduction caused poorly controlled hyperthyroidism, further complicated by severe neutropenia, necessitating discontinuation. In addition, multiple MSUD catabolic crises further complicated the medical management. A total thyroidectomy was planned after metabolic stabilization and preoperative preparation. Perioperative management included Lugol's iodine, hydrocortisone, and propranolol, but hyperthyroidism paradoxically worsened within 24 h due to the iodine effect. Neutrophil count improved with high-dose hydrocortisone; careful reintroduction of low-dose methimazole, with close monitoring of the ANC, resulted in better control of hyperthyroidism. Another perioperative challenge included strict branched-chain amino acid restriction and high-dose insulin infusion to counter hydrocortisone metabolic risk, with careful special "sick days" management guided by a metabolic specialist to prevent neurological sequelae and metabolic crisis. Total thyroidectomy proceeded uneventfully after multidisciplinary optimization. Postoperative transient hypocalcemia was managed conservatively, and levothyroxine replacement was initiated. The patient successfully underwent liver transplantation several months later.