SAT-LB82 Myxedema as Presenting Feature of Profound Primary Hypothyroidism in a Toddler

Background: Myxedema is a rare presenting feature of profound primary hypothyroidism that results from disordered accumulation of glycosaminoglycan in the skin and soft tissue. Very few cases of myxedema have been reported in children during the first few years of life. Clinical Case: A 2-year-old boy with a history of lissencephaly and developmental delay was sent to the emergency room by his primary care physician for worsening of edema. It was noticed by his mother six weeks previously and involved his face, arms, feet and legs. He had no history of cold intolerance, dry skin, hair loss, constipation, or excessive sleep. On exam, he had normal vital signs with no bradycardia and normal blood pressure. Physical exam was remarkable for a sallow complexion, coarse facial features, abdominal distention and non-pitting edema of the face, limbs, hands and feet. A cardiac echo revealed mild pericardial effusion and borderline QT prolongation was noted on EKG. Chest x-ray and abdominal x-ray were unremarkable. Metabolic profile showed normal electrolytes, a mildly low albumin of 2.8 gm/dl and normal renal and liver function. Thyroid function tests were remarkable for an elevated TSH of 562 mcu/ml and a low FT4 of 0.3 ng/dl. TPO and anti-thyroglobulin antibodies were negative. Thyroid ultrasound demonstrated a small thyroid gland in the normal location. Growth data revealed a normal linear growth velocity and weight persistently above the 25th percentile. The child’s newborn screen for congenital hypothyroidism had been normal. He was started on levothyroxine 50 mcg PO per day. Conclusion: We report an extremely atypical presentation of primary hypothyroidism in a two-year-old boy. He presented with myxedema, pericardial effusions, severe biochemical hypothyroidism and negative thyroid antibodies. The precise etiology and duration of his hypothyroidism, as well as its role in his developmental delay, remain enigmatic. Awareness of unusual presenting features in very young children with hypothyroidism is essential in order to achieve expedient treatment and optimal neurocognitive outcomes.