The blocked D phenomenon in haemolytic disease of newborn- A case report of a diagnostic dilemma

The Rh D antigen is highly immunogenic and responsible for the majority of cases of haemolytic disease of foetus and the newborn, particularly in the developing world. Anti D prophylaxis of Rh negative mothers has revolutionized the approach to management of Rh negative mothers bearing Rh positive babies. It is critical in this setting that accurate blood grouping and Rh typing of these mothers and their babies is available to ensure appropriate intervention and clinical management. We describe a case of a 2 day old term infant, born to a multiparous Rh negative mother who was referred to our centre with clinical and laboratory evidence of haemolytic disease of newborn for further management. The mother was B Rh negative, had a positive antibody screen and the red cell alloantibody was identified as anti D. The baby was O Rh negative, and was direct antiglobulin test positive. Given the clinical scenario, the possibility of the blocked D phenomenon was considered. Subsequent appropriate testing including partial elution and regrouping, identified the blood group of the baby to be O Rh positive, confirming the diagnosis of haemolytic disease of foetus and newborn due to Anti D and allowing for appropriate and informed clinical management