Thyrotoxicosis and Impending Thyroid Storm: A Rare Paraneoplastic Syndrome in an Infant With Hepatoblastoma.

Graves' disease is the most common cause of pediatric hyperthyroidism and thyrotoxicosis. Thyroid storm is a rare initial manifestation of Graves' disease and represents an endocrine emergency. We report a case of transient hyperthyroidism, possibly a paraneoplastic syndrome presenting as impending thyroid storm in a patient with undiagnosed hepatoblastoma. To our knowledge, this is the first case of this association reported in children. A previously healthy 21-month-old male presented with abdominal pain and unremitting tachycardia. He was managed for thyrotoxicosis and impending thyroid storm. He subsequently was found to have hepatomegaly leading to a diagnosis of hepatoblastoma. Autoimmune markers for Graves' disease were negative, along with a negative human chorionic gonadotropin. After initiation of neoadjuvant chemotherapy, he had complete resolution of thyrotoxicosis. Paraneoplastic syndromes may occur with any tumor. We present a unique case of a patient developing human chorionic gonadotropin-negative hyperthyroidism, possibly as a paraneoplastic syndrome from hepatoblastoma.