Yellow cerebrospinal fluid in an extremely preterm infant: a case report.

Although phototherapy has reduced the incidence of kernicterus in term infants, it remains a significant threat to extremely preterm infants due to their immature blood-brain barrier and frequent comorbidities such as sepsis. Current clinical practice relies on serum total bilirubin levels, which may not accurately reflect cerebral bilirubin exposure in this vulnerable population. This case report describes an extremely preterm infant (gestational age 28 1/7 weeks, birth weight 950 g) who developed visibly yellow cerebrospinal fluid (CSF) on the first day of life. Despite only minimal serum hyperbilirubinemia (4.4 mg/dL; ≈ 75.2 μmol/L), CSF bilirubin was markedly elevated at 10 mg/dL (≈ 171 μmol/L). The infant presented with respiratory distress syndrome and sepsis. Immediate intensive phototherapy was initiated, leading to the normalization of CSF bilirubin (3.6 mg/dL ≈ 61.5 μmol/L) within 4 days. Brain magnetic resonance imaging (MRI) and automated auditory brainstem response (AABR) performed at the corrected age of 4 months were both unremarkable. At the corrected age of 12 months, neurodevelopmental assessment using the Bayley Scales of Infant Development-III (BSID-III) showed scores within the normal range. This case illustrates that CSF bilirubin can serve as a sensitive early biomarker for identifying preterm infants at imminent risk for bilirubin neurotoxicity, particularly when serum bilirubin levels are misleadingly low. Targeted measurement of CSF bilirubin in selected high-risk infants, when a lumbar puncture is otherwise indicated, could enable more timely intervention and contribute to improved neurodevelopmental outcomes.