Severe myxedema coma and pericardial effusion in a child with Down syndrome: the importance of adherence to levothyroxine therapy.

Myxedema coma is a rare, but life-threatening endocrinological emergency. Myxedema is characterized by altered mental status, and is accompanied by hypotension, bradycardia, hypothermia, bradypnea, hyporeflexia, hyponatremia, and hypoglycemia, all stemming from reduced metabolism due to severe hypothyroidism. Additionally, patients may exhibit signs of low cardiac output, edema in the extremities, peripheral circulatory disturbances, shock, and the development of pericardial and pleural effusions, ultimately leading to confusion and coma. We present a successfully treated case of severe myxedema coma with recurrent pericardial effusion and hypotensive shock. This case is characterized by an unusual clinical presentation and required a distinct treatment strategy highlighting its exceptional rarity.A 2-year-old boy with Down syndrome presented with recurrent pericardial effusion attributed to medication non-adherence. The critically-ill patient, experiencing a severe cardiogenic shock required mechanical ventilation and inotropic infusions in the pediatric intensive care unit. Elevated thyroid stimulating hormone (TSH), and low free T4 (fT4) and free T3 (fT3) levels prompted consideration of myxedema coma. Upon reviewing the patient's medical history, it was ascertained that he had an ongoing diagnosis of primary hypothyroidism, and exhibited non-adherence to the prescribed treatment regimen and failed to attend scheduled outpatient clinic appointments for follow-up assessments. The treatment plan, devised by the pediatric endocrinology team, included the peroral administration of L-thyroxine (L-T4) at a dose of 50 micrograms per day. After beginning regular oral L-T4 treatment, a gradual improvement in the patient's condition was observed. Notably, by the 15th day of oral therapy, the patient had made a full recovery. Contrary to the recommended intravenous treatment for myxedema coma, this patient was successfully treated with oral levothyroxine, due to the unavailability of the parenteral form in Türkiye.This case report presents an instance of non-adherence to L-T4 therapy, which subsequently progressed to severe myxedema coma. Changes in neurologic status and hemodynamic instability in a patient with a history of hypothyroidism should raise the concern of nonadherence and, though rare, myxedema coma should be in the differential diagnosis.