What enzyme deficiency is associated with breast milk jaundice?

Breast milk jaundice is primarily linked to a deficiency in the enzyme glucuronyl transferase, which is crucial for bilirubin metabolism. In newborns, the liver is often immature, leading to a limited ability to conjugate bilirubin effectively. Glucuronyl transferase facilitates the conversion of unconjugated bilirubin into conjugated bilirubin, which is water-soluble and can be excreted from the body through bile.

During breastfeeding, certain substances present in breast milk can inhibit the activity of glucuronyl transferase, worsening the jaundice condition. This phenomenon typically occurs within the first week of life and can manifest as a prolonged elevation of bilirubin levels in infants who are exclusively breastfed. Understanding this mechanism is vital for managing breast milk jaundice, as recognizing the role of glucuronyl transferase allows healthcare providers to reassure parents about the transient nature of the condition and the importance of continued breastfeeding while monitoring bilirubin levels.