Prolonged neonatal jaundice: a manifestation of heterozygote state for Crigler--Najjar syndrome?

A prolonged but transient neonatal jaundice due to unconjugated hyperbilirubinemia was observed in two unrelated babies who were siblings of patients with Crigler--Najjar disease (Arias type I). The bilirubin-UDP-glucuronyl transferase activity measured in the liver of both patients, at the age of 6 and 7 months, respectively, was found to be low, suggesting a permanent deficiency in bilirubin glucuronidation, which might be the expression of a heterozygote state.