International Perspectives: Clinical Kernicterus in Preterm Infants in Japan

In recent years, clinical kernicterus has been diagnosed in preterm infants on the basis of motor (kinetic) disorders such as choreoathetosis and dystonia, impairment in auditory neuropathy-type hearing, and abnormal pallidal signals on head magnetic resonance imaging. In Japan, it is currently estimated that at least 8 to 9 cases of kernicterus (approximately 2 per 1,000 cases) occur annually in preterm infants of less than 30 weeks’ gestation. Therefore, there is an urgent need to revise our jaundice management approach in preterm infants. Two major characteristics of Japanese preterm infants who develop clinical kernicterus are: (1) a peak total serum/plasma bilirubin (TB) level at 2 weeks of age or later; and (2) no markedly high total bilirubinemia. Some patients without high TB levels have high levels of unbound serum/plasma bilirubin (UB). Consequently, we propose that in Japanese preterm infants, continuous monitoring of bilirubin (using transcutaneous bilirubinometry or direct TB measurements) and/or binding status (UB levels or bilirubin-binding capacity) may be necessary.