A Case of Severe Hemolytic Disease of the Newborn Caused by Anti-Di^a and SLC4A1 Gene Analysis in the Family

A 1-day-old newborn with extreme hyperbilirubinemia was found in Dalian Children’s hospital, whose total bilirubin surged to 466 µmol/L (27.3 mg/dL) within 4 h after birth. Coomb’s test (anti-IgG) of the newborn was strongly positive, while initial antibody screening test (Blood and Biological Medicine, Shanghai, China) was negative. The mother had an 11-years-old daughter and a severe hemolytic disease of the newborn (HDN) was suspected in this case. The blood type of the newborn was A, Rh CcDee and her mother was A, Rh CcDEe, so ABO and Rh HDN were excluded. In order to confirm the cause of the hyperbilirubinemia in this newborn, more serological and genetic tests were performed for further investigation in Dalian Blood Center. No antibody was identified in the plasma of both the newborn and her mother by using Makropanel 16 (Sanquin Reagents, Amsterdam, Netherlands). However, anti-Di^a antibody was identified in the newborn’s plasma and eluate of her red blood cells by using Panel Cells 10 (Blood and Biological Medicine, Shanghai, China). An antibody titer of 128 was detected using Di (a+) red cells by the method of double dilution. As inaccessibility of monoclonal anti-Di^a and anti-Di^b reagent, for further investigation, we performed polymerase chain reaction-sequence based typing (PCR-SBT) to genotype DI*A (Di^a) and DI*B (Di^b) [1]. Sequencing for exon 19 of SLC4A1 gene in the family is illustrated in Fig. 1.

Fig. 1.

Sequencing of exon 19 of SLC4A1 gene in the family. Heterozygotes of DI*A (Di^a, 2561T) and DI*B (Di^b, 2561C) alleles were found in the newborn’s paternal grandmother (a), paternal grandfather (b), sister (e) and the newborn (f), whose genotypes were DI*A/DI*B. Homozygote of DI*A (Di^a, 2561T) allele was found in the newborn’s father (c), whose genotype was DI*A/DI*A. Homozygote of DI*B (Di^b, 2561C) allele was found in the newborn’s mother (d), whose genotype was DI*B/DI*B

Hemolytic disease of the newborn happens when mother’s blood group is incompatible with the newborn's. ABO alloimmunization between the mother and newborn is the leading cause of HDN, followed by Rh blood group incompatibility. Antigens of other blood group systems can also elicit immune responses in pregnancy. Diego blood group system is clinically significant in transfusion medicine. The Diego system currently consists of 22 antigens, including 3 pairs of antithetical antigens—Di^a (DI1) and Di^b (DI2), Wr^a (DI3) and Wr^b (DI4), Wu (DI9) and DISK (DI22).The Diego antigens are carried on band 3 anion transport protein, also known as CD233, anion exchanger 1 (AE1) or solute carrier family 4 anion exchanger, member 1 (SLC4A1), which is encoded by the SLC4A1 gene in humans. The SLC4A1 gene, which is located at chromosome 17q12-q21, covers 18 kb of DNA and contains 20 exons. Di^a was first described in a Venezuelan family by Layrisse in 1955 [2]. Di^a is associated with 2561C > T in exon 19 of SLC4A1 gene. Di^a represents Leu854 and Di^b represents Pro854 in band 3 protein. The allele frequency of DI*A (Di^a) in different races vary greatly. Di^a is relatively common in South American Indians (36%) and Asians of Mongolian origin (5–15%), but very rare among Caucasians and Blacks (0.01%) [3–5]. In our study, all the family members were Han ethnic, and Di^a prevalence in Chinese Han population was estimated to be 2.47% [1].

When a newborn is found to have a positive Coomb’s test, but absent of major blood groups incompatibility, technicians should think of the existence of an antibody to a low frequency antigen inherited from the father, such as Di^a. Using more panels of red cells for antibody identification may increase the detection of the rare antibody. In this case, anti-Di^a is a rare antibody which caused the severe HDN. Introduction of Di (a+) red cells to an antibody screening or identification panel is necessary in regions where anti-Di^a is relatively common. The neonate was treated successfully with phototherapy and exchange transfusion. Five days later, she was discharged home in stable condition.

Compliance with Ethical Standards

Conflict of interest

The authors declare no potential conflicts of interest.

Ethical Approval

This study involved human participants and was approved by Ethical Committee of Dalian Blood Center. All the procedures complied with the Declaration of Helsinki.

Informed Consent

All the participants signed the informed consent.