Thymus involution and cerebral white matter damage in extremely low gestational age neonates

Background: Among newborns who die, those who have cerebral white matter damage are more likely than others to have thymus involution and low thymus weights. Objective: We sought to evaluate in a population of preterm newborns who did not die if those who developed a cerebral white matter damage (as defined by an echolucency) are more likely than others to have thymus involution as assessed on chest radiographs. Method: The 89 infants whose data were evaluated were born before the 28th week of gestation, had at least one chest radiograph within the first 2 days of life (to determine thymus size), and at least one cranial ultrasonogram to assess for white matter echolucency. Results: Eighty-five percent of these infants had a small thymus within the first 2 weeks of life. Median time to thymus involution in those born before the 26th week of gestation was 36 h, and in those born during or after the 26th week of gestation was 140 h. Infants who developed involution before the median time in their respective gestational age groups were classified as early involuters (group 1) and were compared to their peers with late/no involution (group 2). Infants with an echolucency were more likely to have had early involution than infants without an echolucency (89% vs. 44%) (p = 0.01). This relationship was not distorted by potential confounders. The echolucency odds ratio associated with early thymus involution was consistently above 8 in all strata of the sample. Conclusion: These results are consistent with the possibility that early thymus involution and neonatal white matter damage are not independent phenomena and may have common antecedents.