Abstract: Objective To investigate the serological characteristics and clinical significance of hemolytic disease of newborn (HDN) caused by the anti-Mur antibody. Methods ABO and Rh blood group typing were done on blood samples from one neonate and their parents. Antibody screening and identification were performed on the blood samples of the neonate and the mother. The neonate's blood sample were subjected to direct antiglobulin test (DAT), serum antibody identification, and elution antibody identification. PCR-SSP was used for MUR gene detection in the blood samples from the neonate and parents. Results The blood types of the neonate, mother, and father were A DCCee Mur+, A DCCee Mur-, and A DCCee Mur+, respectively. IgM-Mur and IgG-Mur antibodies were detected in the mother's serum, while IgG-Mur antibody was found in both the neonate's serum and the elution. The IgG-Mur titers in the mother's serum, the neonate's serum, and the elution were 128, 32, and 64. The neonate's DAT, serum antibody screen, and elution screen were all positive. Jaundice occurred in the infant shortly after birth, with the bilirubin level peaking at 221.9 μmol/L, and the jaundice gradually subsided following treatment with phototherapy and intravenous administration of human immunoglobulin. Conclusion In cases of hemolytic disease of newborn test, if antibody screening is negative for both the mother and the neonate, but the neonate's DAT is positive and there are clinical signs of hemolysis, the possibility of low-frequency antibodies, such as anti-Mur, should be considered. Laboratories are encouraged to use panel cells containing rare antigens for antibody identification and combine molecular typing technology to prevent missed diagnoses and ensure the safety of both mother and neonate.

Key words: Anti-Mur antibody, Low-frequency antibody, Neonatal hemolytic disease