The Kidd blood group is a major antigenic system in human erythrocytes, and this antigen system is defined by two antithetical specificities, Jka
, and a third rare recessive gene, Jk, that produces neither Jka
). The Kidd antigens are localized on a 43 kDa red blood cell integral membrane protein that functions as a urea transporter (8
are alternate, autosomally inherited codominant alleles. The Kidd blood group is clinically significant since Jk antibodies can cause acute and delayed transfusion reactions as well as HDN.
was first described by Plaut et al. in 1953 (5
). Most of the reports on anti-Jkb
have stated that this condition followed after repeated blood transfusions (9
). The first case of anti-Jkb
related HDN was reported by Kornstad and Halvorsen in 1958 (11
). Up to the present time, only eleven cases of anti-Jkb
related HDN have been reported in the medical leterature. Although approximately 20-29% of the Caucasian and Asian population have the phenotype Jk(a+b-) (12
), introduction of the Jkb
antigen into such individuals is rarely associated with clinically manifesting disease. This is apparently due to the fact that Jkb
is a poor antigen. summarizes the pertinent clinical and serologic data concerning the cases of HDN due to anti-Jkb
that have been reported to date (15
). In all the reported cases, the disease was usually mild to moderate with a benign prognosis. Although all the infants exhibited a strongly positive direct Coombs test, any anemia was either absent or present to only a slight degree.
Summary of the clinical and laboratory data from the published cases of hemolytic disease of newborn due to anti-Jkb
An additional case of HDN that was apparently due to anti-Jkb
has been reported by Kanner (23
). This case radically differs from those reported previously in that the woman's third baby was "very jaundiced and anemic", and the baby died at the second day after birth. No other information about the baby was reported. This case has not been included in because of insufficient data. The baby in our case was also severely affected at the time of admission and she suffered the neurologic consequences of kernicterus. Despite the medical management with exchange transfusion and intensive phototherapy, the baby died of intractable seizure and acute renal failure at the fourth day after admission.
The pathogenesis of HDN due to anti-Jkb
is similar to that of other antibodies. Maternal alloimmunization occurs when a woman's immune system is sensitized to foreign erythrocyte surface antigens that stimulate the production of immunoglobulin G (IgG) antibodies. The most common routes of maternal sensitization are via blood transfusion or by fetomaternal hemorrhage (transplacental passage of fetal erythrocytes), which is associated with delivery, trauma, spontaneous or induced abortion, ectopic pregnancy or invasive obstetrical procedures. In the event of a pregnancy subsequent to becoming alloimmunized, these antibodies can cross the placenta and result in hemolysis of fetal erythrocytes and also anemia, which in turn can lead to potentially disastrous consequences for the fetus (24
). Our case and Kanner's cases differ from other reported cases on the maternal history; Kanner's and our case involved the third baby. The first and second babies had been jaundiced, yet they had never been transfused with blood, plasma or any blood derivatives. Therefore, the anti-Jkb
antibody production apparently was initiated at the time of pregnancy. We can suggest that both women had three babies with HDN due to anti-Jkb
Although HDN of anti-Jkb incompatibility is rare malady that generally shows mild clinical symptoms and a favorable prognosis, we experienced the second apparent case of HDN due to anti-Jkb that had severe clinical symptoms and a fatal outcome. Therefore, HDN due to minor blood group instability must be ruled out for all the cases of jaundice occurring 24 hr after birth. Screening and quantification of irregular antibodies are required for early diagnosis as a medical measure to prevent kernicterus through phototherapy and exchange transfusion, and close attention should be paid for possible delayed hemolytic anemia.
As a therapeutic measure, prenatal genotyping for Jkb
of the fetal amniotic cells should be done to identify those high risk pregnancies with HDN that are due to anti-Jkb
incompatibility, and the genotyping can be done by allele-specific polymerase chain reaction. An allele-specific polymerase chain reaction (ASPCR) assay for prenatal genotyping of the Kidd antigen system in order to identify pregnancies at risk for HDN was developed. The availability of this assay, which can accurately genotype the Kidd blood group system, even in the presence of extensive maternal contamination, provides an important tool in managing pregnancies at risk for Kidd-related HDN (14
). For the high risk fetus, intrauterine exchange transfusion (25
), serial follow up of the serum bilirubin level and the use of erythropoietin for anemia (26
) should be considered.