Unexplained Late-Onset Hemolytic Jaundice Preceded by High Fetal Hemoglobin Level in an Extremely Low Birth Weight Infant

BACKGROUND: Preterm infants sometimes have transient late-onset hemolytic jaundice; however, the etiology has yet to be determined. CASE PRESENTATION: In our case, fetal hemoglobin (HbF) level increased significantly to 100% at 23 days of age. Levels of methemoglobin and carboxyhemoglobin also increased to 2.9% and 3.5%, respectively, following the elevated HbF level. At 26 days, hemolytic jaundice developed. No abnormality of red blood cell membranes and enzyme activities was found. CONCLUSIONS: The etiology of late-onset hemolytic jaundice in preterm infants may associate with an impaired switching from HbF to adult hemoglobin (HbA) or reverse switching from HbA to HbF.