Transient hypoglycemia with hyperinsulinemia in a newborn infant with Rubinstein-Taybi syndrome.

A newborn boy with Rubinstein-Taybi syndrome who had profound neonatal hypoglycemia is presented. The infant was a discordant fraternal twin with intrauterine growth retardation. The hypoglycemia was due to transient hyperinsulinemia, a condition often seen in small-for-gestational-age infants. Neonatal hypoglycemia may be common in infants with Rubinstein-Taybi syndrome, especially if they also have intrauterine growth retardation.