A 3-day-old full-term male newborn is brought to the physician by his mother because of a 24-hour history of yellow skin. He appears healthy. Physical examination shows mild jaundice. Laboratory studies show a hemoglobin concentration of 17 g/ dL and a total serum bilirubin concentration of 10 mg/dL, with an indirect component of 8 mg/dL. The jaundice resolves 5 days later. A deficiency of which of the following is the most likely cause of the jaundice in this patient?

Question

Quizplus · Accepted Answer

The jaundice in this newborn is likely due to physiological neonatal jaundice, which is caused by a transient deficiency of hepatic UDP-glucuronyltransferase activity. This enzyme is responsible for conjugating bilirubin, and its activity is low in newborns, leading to an increase in unconjugated (indirect) bilirubin. Excess circulation and accumulation of bilirubin (hyperbilirubinemia) results in a yelloworange discoloration of the tissues and is most easily visible as icteric (yellowish) discoloration in the sclera of the eyes. These symptoms are referred to as jaundice. There are several causes of jaundice including defects in the enzyme responsible for bilirubin conjugation to glucuronic acid, bilirubin UDP-glucuronyltransferase (bilirubin-UGT).

A 3-Day-Old Full-Term Male Newborn Is Brought to the Physician