Singhania N*, Vaidya A**, Gupta AS***.
(* Junior Resident, ** Senior Resident, *** Professor, Department of Obstetrics and Gynecology, Seth G S Medical College and K E M Hospital, Mumbai, India.)
A blood group is called rare when it is found in a frequency of 1:1000 samples of a given population. Rare blood groups are those who lack high frequency antigens. Anti-Rh17 is a rare alloantibody produced after an immune stimulus like blood transfusion or pregnancy, by individuals who lack C/c and E/e antigens of Rh blood group on their red cells. This rare blood group is denoted as D- -. We report diagnosis and management of a pregnant lady with anemia, monchorionic diamniotic twins and presence of anti-Rh17 alloantibodies.
Rare blood groups are those who lack high frequency antigen in relation to blood transfusion and they occur with a frequency of 1:1000 samples of a given population. Rare blood type may vary from country to country and therefore a blood type rare in one country may not be considered rare in another. The following rare blood types were encountered over a period in India; “Bombay” (Oh) phenotype, D -/- D -, In(a+b-), Co(a-b-), weaker variants of A, B and H antigens, I-i-, CdE/CdE (ryry) and Mg. Anti-Rh17 is a rare alloantibody. This rare blood group is designated as D- - and was first described by Race and Sanger in 1950.
A 25 year old primigravida, a nurse by profession with monchorionic diamniotic twins registered in the antenatal OPD at 10 weeks of pregnancy. She had regular antenatal visits. Her booking hemoglobin (Hb) was 11.4 mg/dl. At 24.5 weeks of gestation she was admitted in view of threatened preterm labor. Tocolysis was given. In her routine investigations, she was found to be anemic with Hb of 8.5 mg/dl, total leucocyte count (TLC) was 10,700/mm3, and platelet count was 3.2 lacs/cu mm. Serum ferritin was 10.48 ng/ml. Serum bilirubin was within normal limits. Serum LDH was 660 IU/liter. Peripheral smear was suggestive of anisocytosis, poikilocytosis, hypochromia, microcytosis, macrocytosis, target RBC’s with Rouleax formation. Hb electrophoresis showed no abnormal hemoglobin’s. All other investigations were within normal limits. Parenteral iron therapy was initiated but there was no improvement even after 2 weeks. Hemoglobin was persistently low. The blood grouping report was suggestive of autoantibodies. Hematologist opinion was taken and was advised to do husband’s blood group. Extended blood group typing and antibody panel with temperature sensitivity was also advised. Husband’s blood group was B positive. Extended blood grouping suggested ABO blood group to be B with Rh group to be D--/D--. All her family members were tested for this rare blood group and only her younger teenage sibling was found to have similar group. No donor was available for her. Hemoglobin was serially monitored every 2 weeks and fetal surveillance was done to rule out fetal anemia by serial ultrasonography for MCA PSV. She was continued on parenteral iron, vitamin B12 and folic acid therapy. Her hemoglobin raised to 12.4 mg/dl. Serial ultrasonography for MCA PSV done every 2 weekly showed a rising trend but was always less than 1.5 mean over median (MOM). At 30.3 weeks of gestation she went into inevitable preterm labor. Tocolysis was stopped. Transfusion medicine consultant advised not to transfuse any products containing RBC’s. Plasma products like FFP, platelets and cryoprecipitate can be given. She delivered vaginally with first twin, male child of 1.586 kg by vertex presentation and second twin, male child of 1.620 kg by breech extraction. Apgar score was 9/10 for both babies. Postpartum hemorrhage prophylaxis with oxytocin and injection methylergometrine were given. There was no postpartum hemorrhage and no blood transfusion was required. Babies were kept in NICU for low birth weight. There blood groups were B positive (both of them). Later on the babies were discharged from NICU uneventfully.
Rh17 is a sub type of Rhesus blood group. The Rh blood group system has two Rh genes (D and CE). Four combinations are possible by CE. These can be CE, Ce, cE or ce. Absence of this cDe is referred to as Rh17. It is a high frequency antigen negative blood. Anti-Rh17 (anti-Hro) is a monospecific IgG alloantibody, which reacts with a common determinant on the Rh-CE protein, generally found in patients with history of blood or blood products transfusion or pregnancy. The genetic events producing the D-- phenotype are not yet understood. According to a case report published by Huang CH et al, recombination of portions of the Rh-D gene with the Rh-CE gene leads to overexpression of Rh-D antigens and the lack of Rh-CE antigens, thus producing Rh17. The same case report also stated that this particular phenotype can be inherited by compound heterozygosity also, apart from consanguineous homozygosity, hence all blood relatives of the patient should be screened for a similar blood group. A total of 3 cases of anti-Rh17 allo-immunisation have been reported in English literature and 40 cases in Japanese literature till now. According to a study by Yun JW et al even trivial amounts of RBCs in platelet concentrates can also trigger sensitization to the highly immunogenic C, c, E, or e antigens and induce the formation of anti-Rh17 and other Rh antibodies. Since our patient is nurse by profession we speculate that needle prick injury could be the source for exposure to trivial amount of RBCs, thus triggering sensitization in our patient. Surgery is usually contraindicated in such cases but if required, intraoperative blood saving units should be used or appropriate donors having same blood group or Rh-null RBC’S can be transfused. A few cases have been reported using exchange transfusion postpartum to decrease the number of antibodies but it did not prove to be very efficacious. Past literature reviews have concluded that Anti-Rh17 are known to produce hemolytic disease of the new-born which ranges from mild to fatal. Fetal anemia should be monitored throughout pregnancy and if required intrauterine transfusions should be given with frozen rare donor blood or maternal blood.
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Singhania N, Vaidya A, Gupta AS. Alloimmunisation with rare blood group in twin pregnancy. JPGO 2019. Volume 6 No.4. Available from: https://www.jpgo.org/2019/04/alloimmunisation-with-rare-blood-group.html