Hypothyroidism secondary to chronic lymphocytic thyroiditis has an increased prevalence among individuals with Down's syndrome.1-3 However, the onset of thyroid disease is typically during childhood or the early adult years and only two neonatal cases have been reported.4-5 Therefore, we wish to describe an infant with trisomy 21 in whom hypothyroidism was diagnosed at 13 days of age, the third such case to be reported. This patient also provides an opportunity to emphasize the distinguishing clinical features of these two conditions in infancy.
Report of a Case.—This female infant was born after approximately 37 weeks of gestation to a 23-year-old gravida 3, para 2, mother. No medications were taken during the uneventful pregnancy. Delivery was by cesarean section after prolonged labor due to cephalopelvic disproportion. Birth weight was 3.05 kg and length was 46 cm. Three days after birth the patient was noted to be hypothermic and jaundiced and to