A Rare Case of a Newborn with Blocked RhD Antigen Caused by Low-Titer Antibody.

BACKGROUND: Hemolytic disease of the fetus and newborn (HDFN) is a condition characterized by severe hemolysis and anemia in fetuses or neonates. To our knowledge, this is the first reported case of a newborn with blocked RhD antigen caused by low-titer antibody. METHODS: Peripheral blood samples were collected from the newborn upon admission. ABO and RhD blood typing was performed using a microcolumn gel agglutination test. Direct antiglobulin test (DAT) was performed using polyspecific anti-human globulin. Indirect antiglobulin test (IAT) was used to screen for irregular antibodies in the serum. Thermal elution was carried out by incubating the newborn's red blood cells at 56℃ for 10 minutes, and the resulting eluate was tested for non-ABO antibodies and their titers by IAT. RESULTS: At birth, the infant was typed as O Rh-positive. However, pre-transfusion retesting indicated O Rh-negative status. The DAT was negative, whereas the IAT was positive (2+). Subsequent ABO-compatible elution testing also yielded a positive result (1+). The antibody titer was measured at 1:16. CONCLUSIONS: This is the first reported case of blocked RhD antigen caused by low-titer antibody. This case high-lights the critical importance of comprehensive serological investigation in affected neonates to guide appropriate clinical management and transfusion strategy.