Nationwide survey of late‐onset hemolysis in very low birthweight infants

BACKGROUND: In Japan, some cases of late‐onset acute hemolysis in very low birthweight (VLBW) infants have been reported. These cases had common features but the cause of hemolysis was unknown. The incidence and prognosis of this disease are also unknown. However, there are only few reports of such hemolytic episodes in countries other than Japan. Thus, this study aimed to examine the incidence and clinical course of late‐onset acute hemolysis and to establish it as a new disease concept. METHODS: A nationwide prospective survey was conducted from 2011 to 2015 as a rare disease surveillance project of the Japan Society for Neonatal Health and Development. RESULTS: Twenty‐four cases were confirmed. The median (range) gestational age, birthweight, and onset of hemolytic episodes were 26 weeks and 2 days (23 weeks and 4 days–31 weeks and 2 days), 898 g (627–1,416 g), and 19 days after birth (9–33 days), respectively. Phototherapy, blood transfusion, and exchange transfusion were required in 22 (96%), 24 (100%), and 7 (29%) cases, respectively. During the observation period, no recurrence of the hemolytic episode occurred. All patients survived; however, one case developed kernicterus and suffered severe neurological sequelae. CONCLUSIONS: In this study, at least 1 out of 1,259 VLBW infants developed hemolysis at 9–33 days after birth in Japan. Owing to the risk of kernicterus, this disease should be recognized as among the important pathological conditions of VLBW infants, suggesting the need to manage jaundice and anemia until 5 weeks after birth.