A new case study published in Transfusion highlighted how hidden blood type variants can lead to hemolytic disease of the fetus and newborn (HDFN), underscoring the need for more precise testing in pregnancy care.
The report described a 26-year-old Argentinean woman who appeared to have a normal D-positive blood type during routine prenatal screening. But later genetic testing revealed that she actually carried a partial D variant known as RHD*14.02, or the DBT phenotype.
Because commercial tests detected her as D-positive, she did not receive Rh immunoglobulin prophylaxis, which is normally given to prevent immune reactions. As her pregnancy progressed, her immune system produced high levels of anti-D antibodies against the missing parts of the D antigen. These antibodies crossed the placenta and destroyed her baby’s red blood cells, causing a severe case of HDFN.
The woman delivered the baby by emergency cesarean section at nearly 38 weeks after her doctors detected signs of fetal distress. At birth, the infant had dangerously high bilirubin levels and required an immediate double-volume exchange transfusion. Following treatment, the baby stabilized and was discharged in good health five days later.
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Further testing of the mother’s family showed that her father and one brother also carried the RHD*14.02 variant, although each had one normal allele as well. The family received genetic counseling to inform them of the inheritance pattern and the possibility of passing the variant on to future children.
Partial D variants like DBT are difficult to detect with standard serologic testing, which often shows strong positive results indistinguishable from typical D-positive samples. Yet, these individuals remain at risk of forming dangerous antibodies if exposed to conventional D-positive red cells through pregnancy or transfusion.
The authors noted that while molecular testing is more costly than routine blood typing, it can prevent missed diagnoses and avoid severe complications like HDFN.
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