Symptomatic Hypercalcemia with Vomiting in a Pediatric Patient with Graves' Disease.

Graves' disease (GD) is the leading cause of childhood hyperthyroidism, resulting from excessive thyroid hormone production. In some cases, it can cause alterations in mineral homeostasis, including calcium, phosphorus, and magnesium, which are often overlooked. Hyperthyroidism increases osteoclastic bone resorption, and mild to moderate hypercalcemia occurs in approximately 20-50% of affected patients, typically resolving with appropriate therapy. Although uncommon, symptomatic hypercalcemia in the setting of GD requires immediate evaluation and management. An 8-year-11-month-old girl was brought to the clinic, presenting with recurrent nausea, vomiting, and fatigue. She had multiple hospital admissions over the previous seven months due to drug reaction with eosinophilia and systemic symptoms (DRESS) and acute inflammatory demyelinating polyneuropathy (AIDP). Blood tests showed hyperthyroidism, marked hypercalcemia and hypomagnesemia. She showed tachycardia and weight loss. Based on the Burch-Wartofsky Point Scale, she was diagnosed with impending thyroid storm. Treatment was initiated with intravenous hydration, furosemide, dexamethasone, along with oral methimazole and propranolol. Within a few days, her general condition improved, her heart rate decreased, and gastrointestinal symptoms resolved and serum calcium levels normalized. Follow-up tests showed stable thyroid function and normal calcium levels. This case highlights that symptomatic hypercalcemia associated with GD and suggests that hyperthyroidism should be considered in the differential diagnosis of unexplained persistent nausea and vomiting.