A term newborn with hemolytic disease develops lethargy, poor feeding, and opisthotonus. Serum unconjugated bilirubin is 28 mg/dL. Bilirubin staining of basal ganglia occurs in this setting because:

• A Neonatal CSF production exceeds absorption, forcing bilirubin into brain tissue
• B The neonatal blood-brain barrier is immature and permits bilirubin entry ✓
• C Unconjugated bilirubin is actively transported across the adult-type barrier by organic anion transporters
• D Neonatal cerebral vessels lack autoregulation, allowing passive bilirubin leakage

Explanation

Kernicterus reflects the immaturity of the neonatal blood-brain barrier, whose tight junctions and transport systems are not fully developed, allowing lipid-soluble unconjugated bilirubin to enter the basal ganglia and brainstem nuclei. In adults the intact barrier excludes bilirubin even at high serum levels unless it is damaged. Neither CSF dynamics nor failure of autoregulation accounts for selective nuclear staining.

Reference: Nelson Textbook of Pediatrics, 22nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.