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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.