 Infants may have a developmental deficiency in UDP-glucuronyl transferase, and are unable to hepatically metabolize the antibiotic drug chloramphenicol which requires glucuronidation.This leads to a condition known as gray baby syndrome.Causes of unconjugated hyperbilirubinemia are divided into three main categories, namely, excessive bilirubin synthesis, liver bilirubin uptake malfunction, and bilirubin conjugation compromise.