Blocked Rhesus (D) antigen in successive pregnancies: A Rare diagnostic pitfall in hemolytic disease of the fetus and newborn

We report the first documented occurrence of the blocked Rhesus (Rh)(D) antigen phenomenon in two successive pregnancies of the same alloimmunized Rh(D)-negative mother. This rare phenomenon can result in false Rh(D)-negative typing of an Rh(D)-positive neonate and pose significant diagnostic challenges in hemolytic disease of the fetus and newborn (HDFN). A 25-year-old Rh(D)-negative woman delivered a term male neonate who developed jaundice and anemia shortly after birth, requiring phototherapy and red cell transfusions. Initial blood grouping by conventional tube technique and column agglutination technology identified the neonate as O Rh(D)-negative despite a strongly positive direct antiglobulin test. Further immunohematological evaluation, including acid elution and dithiothreitol and cysteine-activated papain treatment of neonatal red cells, demonstrated anti-D coating of erythrocytes and confirmed the blocked Rh(D) antigen phenomenon. Repeat evaluation at 1 month of age reconfirmed the diagnosis. Review of obstetric records revealed that a previous sibling had exhibited an identical clinical and laboratory profile, including false Rh(D)-negative typing and anti-D identified in eluate. Failure to recognize this entity may lead to misclassification of neonatal Rh(D) status and delayed diagnosis of HDFN. Awareness of this phenomenon and a systematic immunohematological workup are essential for accurate diagnosis and optimal neonatal management.