MDPI Acta Medica Okayama 2227-9059 11 1 2023 Longitudinal Measurement of Histidine-Rich Glycoprotein Levels in Bronchopulmonary Dysplasia: A Pilot Study 212 EN Daisaku Morimoto Department of Pediatrics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Yosuke Washio Department of Pediatrics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Kei Tamai Division of Neonatology, Okayama Medical Center, National Hospital Organization Takeshi Sato Department of Pediatrics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Tomoka Okamura Department of Pediatrics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Hirokazu Watanabe Department of Pediatrics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Yu Fukushima Division of Neonatology, Okayama Medical Center, National Hospital Organization Junko Yoshimoto Department of Pediatrics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Misao Kageyama Division of Neonatology, Okayama Medical Center, National Hospital Organization Kenji Baba Department of Pediatrics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Hirokazu Tsukahara Department of Pediatrics, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University Histidine-rich glycoprotein (HRG) has been reported to inhibit signaling leading to the release of high mobility group box 1 protein, a damage-associated molecular pattern. The present study aimed to determine the longitudinal change in HRG levels in extremely preterm infants and assess whether complications such as bronchopulmonary dysplasia (BPD) were associated with differences in HRG levels. In this multicenter, prospective, observational study, we measured serum HRG levels every 2 weeks from birth to 8 weeks of age. Serum HRG was measured using an enzyme-linked immunosorbent assay. We included 19 extremely preterm infants in the study and 74 samples were analyzed. The median gestational age was 26.0 weeks, and the median birth weight was 858 g. Serum HRG levels showed a significant upward trend after birth (p < 0.001); median HRG concentrations at birth and at 2, 4, 6, and 8 weeks of age were 1.07, 1.11, 2.86, 6.05, and 7.49 mu g/mL, respectively. Onset of BPD was not associated with differences in serum HRG levels. Further, the serum HRG levels increased significantly after birth in extremely preterm infants. No potential conflict of interest relevant to this article was reported.