Pancytopenia due to suppressed hematopoiesis in a case of fatal hemolytic disease of the newborn associated with anti-K supported by molecular K1 typing

Approach to Pregnancy Affected by Kell Alloimmunization

Hemolytic disease of the fetus and newborn (HDFN) is the development of anemia, hyperbilirubinemia, and finally hydrops fetalis in the fetus when antibodies to antigens on the surface of erythrocytes are transferred from the placenta to the fetus. The most common cause is D-HDFN. K (KEL1) from the Kell blood group system is the most potent immunogenic antigen after D among all blood group antigens. K-HDFN occurs in 0.1-0.3% of pregnant women. It accounts for 10% of cases of antibody-mediated severe fetal anemia. We present a successful management of Kell alloimmunization in a pregnant woman who had 3 times pregnancy loss with hydrops fetalis due to K-HDFN and who was proven to have K-HDFN in the postnatal period in her last pregnancy.

Distribution of Kell phenotype among pregnant women in Sokoto, North Western Nigeria

Introduction

Kell antigen is highly immunogenic and is the common cause of antibody production in mismatched blood transfusions, haemolytic transfusion reaction (HTR) and maternal alloimmunization, which causes severe anaemia in neonates. The aim of this study is to determine the prevalence and ethnic variation of the Kell phenotype among pregnant women in Sokoto, Nigeria.

Methods

Kell antigen status of 150 pregnant women aged 18-45 years and mean age 27.19 ±4.69 years attending antenatal clinic in UDUTH Sokoto Nigeria was determined using the conventional tube method and anti-Kell reagents (Lorne Laboratories, UK).

Results

Among the 150 subjects studied, 3 (2.0%) of subjects were positive and 147 (98.0) were negative for K antigen. Of the 150 pregnant subjects; 32 (21.3%) were primigravidae while 118 (78.7%) were multigravidae. Kell phenotype was more prevalent among primigravidae (3.1%) compared to multigravidae (1.7%) women. The distribution of Kell phenotype among the pregnant subjects was compared based on ethnicity. The prevalence of Kell antigen was significantly higher among the Hausa ethnic group (3.2%) compared to other ethnic groups which indicated zero prevalence (p = 0.001). Kell negative phenotype was ≥ 96.8% among all the ethnic groups.

Conclusion

Our observed prevalence of Kell phenotype is consistent with previous studies among Blacks and Asians but significantly lower than values observed in previous studies among Caucasians. We recommend that all pregnant women should be screened for the presence clinically significant red cell antigens including Kell antigen on their first antenatal visit. Kell negative red cell should be routinely provided for all pregnant women and women with child bearing potential to reduce the risk of Kell-associated HDFN. There is need to introduce routine screening of pregnant women for clinically significant red cell antibodies to facilitate the effective management of HDFN as well as prevent HTR. There is also need for sustained health education of pregnant women in the area to encourage early booking for antenatal care.

[A KEL*02mod allele responsible for an apparent maternity exclusion]

The patient's rare KEL:1,-2 phenotype was highlighted in course of a routine preoperative erythrocyte typing. Unexpectedly, her two daughters presented a KEL:-1,2 phenotype what appeared first as an apparent maternity exclusion. Flow cytometry, genotyping and adsorption-elution analyses were then performed for those three patients. KEL genotyping showed that the patient's genotype was KEL*01/KEL*02 whereas that of her daughters was KEL*02/KEL*02. By using polyclonal anti-KEL2 reagent, weak amount of KEL2 was identified on the patient's erythrocytes, a result which was confirmed by both flow cytometry and adsorption-elution assays, suggesting that patient's phenotype was in fact KEL:1,2w. These results are in favour of a weak expressed KEL*02 allele (KEL*2mod) transmission coding for a KEL2 antigen detected in some technical conditions only. Those results allowed to explain the apparent maternity exclusion based on initial KEL phenotype. This study also seems to confirm the presence of a compensatory mechanism of the KELmod allele deficient expression in heterozygote patients. A KEL phenotype retrospective study of 80,000 subjects showed a local KEL:1,-2 frequency four times lower than that described in literature. Moreover, a significant number of those individuals would in reality be KEL:1,2w, what still would decrease the real frequency of the KEL:1,2 subjects.

Neutropenia in infants with hemolytic disease of the newborn

BACKGROUND

This study examined the incidence, outcome and risk factors of neutropenia in infants with hemolytic disease of the newborn (HDN).

METHODS

A retrospective chart review was performed on infants with HDN.

RESULTS

Of 69 evaluable infants, 45% developed neutropenia. Only one infectious complication was recorded. In most instances the neutropenia resolved spontaneously, but in seven infants it persisted for a median of 397 days. Males were at higher risk for developing neutropenia, but severity of HDN, antibody specificity, or therapy were not significant risk factors.

CONCLUSIONS

Neutropenia is a common feature of HDN, regardless of severity of disease, treatment received, or antibody specificity.

Rhesus haemolytic disease of the newborn: Postnatal management, associated morbidity and long-term outcome

Rhesus haemolytic disease of the newborn can lead to complications such as hyperbilirubinaemia, kernicterus and anaemia. Postnatal management consists mainly of intensive phototherapy, exchange transfusion and blood transfusion. During the last decades, significant progress in prenatal care strategies for patients with Rhesus haemolytic disease has occurred. New prenatal management options have led to a remarkable reduction in perinatal mortality. As a result of the increase in perinatal survival, attention is now shifting towards short-term and long-term morbidity. This review focuses on the management of neonatal and paediatric complications associated with Rhesus haemolytic disease, discusses postnatal treatment options and summarizes the results of studies on short-term and long-term outcome.

Genetic diversity of KELnull and KELel: a nationwide Austrian survey

BACKGROUND

Besides ABO and RH, the KEL blood group system, including the two antithetical antigens KEL1 and KEL2, is the most important owing to the frequent appearance of anti-KEL alloantibodies and their considerable clinical significance. So far, only limited information was available on KEL variant alleles determining the rare silent KELnull and KELel phenotypes with absent or diminished KEL antigen expression detected only by adsorption-elution techniques, respectively.

STUDY DESIGN AND METHODS

For a systematic investigation of the KELnull and KELel phenotypes, 401 KEL:1,-2 samples (representing 2.6% of all Austrian KEL:1,-2 samples) and 811 KEL:1,2 samples were genotyped for the KEL*1/KEL*2-specific single-nucleotide polymorphism. All heterozygous KEL*1/KEL*2 and 4 additional KELnull samples were subjected to detailed immunohematologic examination and allele-specific sequencing.

RESULTS

In 14 KEL:1,-2 samples, discrepant KEL*1/KEL*2 heterozygosity was observed, indicating the presence of silent or barely expressed KEL*2 alleles, whereas all KEL:1,2 individuals were homozygous for KEL*2. In the course of further molecular analysis, 8 novel KEL*2null and 2 KEL*2el alleles were discovered, representing 67 and 33 percent of previously known KEL*2null- and KEL*2el-encoding alleles, respectively. In addition, two different known KEL*2null and KEL*2el alleles each were confirmed. The immunohematologic properties of KEL variant red blood cells were defined by extended KEL phenotyping and flow cytometric KEL1, KEL2, KEL4, and KEL7 antigen as well as total Kell protein quantification.

CONCLUSION

For the first time, exact KELnull and KELel population frequencies could be established in this population.

Blood product replacement in the perinatal period

OBJECTIVE

In this article, we will describe some of the special compatibility testing procedures and blood component preparation and modification techniques used in intrauterine and neonatal transfusion medicine. We also will review the transfusion therapy used in hemolytic disease of the fetus and newborn (HDFN) and fetal and neonatal alloimmune thrombocytopenia (FNAIT).

FINDING

Transfusion therapy in the fetus and neonate requires blood typing and compatibility testing techniques not routinely used for adults. These include: cord blood testing, special attention to the volume and speed of infusion, cytomegalovirus risk reduction, and routine irradiation of cellular blood components. The treatment of HDFN and FNAIT involves phenotyping and/or genotyping of fetal and paternal red blood cells and platelets. In FNAIT, platelet products are chosen based on the absence of platelet-specific antigens.

CONCLUSION

Fetal and neonatal transfusion medicine require special attention to the unique anatomic and physiologic features of early human development.