Case 104 Part 2 | Clinical Pathology Unknown Conference

1. Presented by Caroline Early, MD and reviewed by Mark Marzinke, PhD

An otherwise healthy exclusively breastfed newborn infant born at term with appropriate weight-gain develops jaundice during hospital admission following an uncomplicated delivery. Labs reveal an elevated serum total bilirubin of 15.5 mg/dL. The patient is started on phototherapy to prevent bilirubin-induced encephalopathy ("kernicterus") while the etiology of the hyperbilirubinemia is investigated. Workup reveals the following: direct bilirubin 0.2 mg/dL (normal), hemoglobin 10.8 g/dL (low), DAT/Coombs test is negative, reticulocyte count is 5% (elevated), and microspherocytes and "bite" cells are seen on peripheral blood smear. The newborn screen is negative. The patient's blood type is O positive and the mother is O negative. This is the mother's first pregnancy, and prenatal care was at a location other than the hospital where the infant was delivered. She recalls receiving antibiotics for a UTI, but does not know whether she received Rhogam during the pregnancy.

2. After confirming the most likely diagnosis, and in addition to administering Rhogam, what is the most appropriate recommendation to give the mother?

A. Switch to breast-feeding

B. Supplement formula with glucuronidase inhibitors

C. Avoid giving the patient certain medications and foods

D. Prepare for the patient needing lifelong phototherapy