Neonatal testing leading to the identification of B_h (para-Bombay) phenotype in the mother: case report with review of the literature

Abstract

Para-Bombay is a rare phenotype with a homozygous nonfunctional FUT1 gene and a normal FUT2 gene leading to H-deficient red blood cells (RBCs) with or without ABH substances, depending on inheritance of the ABO gene. This case is about a 5-day-old male baby suffering from sepsis who required a 45-mL packed RBC transfusion. The baby's sample tested as A 1 B, D+ and mother's sample tested as group O, D+ with group 4 discrepancy due to ABO isoagglutinins. Further workup of the mother's sample with anti-H lectin was negative, which suggested the mother to be group O h , D+. Antibody screening was panreactive with negative autocontrol, suggestive of anti-H. The titer of immunoglobulin (Ig)M anti-H was 64, IgG titer using dithiothreitol was 8, and anti-IH was absent. A negative adsorption and elution test suggested that RBCs were devoid of A and B antigens. The father's sample tested clearly as group A 1 , D+; hence, the cis-AB blood group was ruled out in the baby. The secretor study of the mother's saliva revealed the presence of B and H substances that neutralized polyclonal B and H antisera. Therefore, we concluded that the mother was of the para-Bombay (B h ) phenotype. This case highlights the importance of reverse grouping and resolving blood grouping discrepancies between mother and child-in this case because of an incongruous ABO blood type of the baby and the mother who was previously tested as group O, D+.