Third nationwide survey of bilirubin encephalopathy in preterm infants in Japan

To determine the clinical features and trends of occurrence of bilirubin encephalopathy in preterm infants (pBE) in Japan.

We conducted a third retrospective nationwide questionnaire-based survey (2024) on pBE in Japan. We performed a two-step questionnaire survey similar to the previous two nationwide surveys. The initial survey determined the number of children born after 2000 who were newly diagnosed with pBE after the 2021 survey. Using a structured questionnaire, the secondary survey clarified the clinical manifestations and characteristics of children with pBE, including demographic data, neurological symptoms, and magnetic resonance imaging (MRI) and auditory brainstem response (ABR) findings. Results were then compared between the three surveys (2017, 2021, and 2024).

An initial survey identified 11 patients with pBE from six institutions. After excluding one patient included in previous studies, clinical information was collected from 10 patients (six boys and four girls) during the secondary survey. The median gestational age was 27 weeks and the median birth weight was 1028 g. Head control and functional gait were observed in 50% and 20% of the patients, respectively. Purposeful hand use and verbal communication were observed in 30% and 40% of patients, respectively. MRI showed T2 hyperintensities in the globus pallidus in nine of nine patients. ABR abnormalities were present in four of four patients. None of the variables differed significantly between the 2017, 2021, and 2024 surveys.

The clinical characteristics of pBE were consistent across the three surveys. Infants with pBE had severely impaired gross motor function but relatively preserved manual function and verbal communication. MRI and ABR findings can aid in the diagnosis of pBE.