NYU Langone Health Baltimore, New York, United States
Background/Case Studies: While alloantibodies against Jka and Jkb antigens in the Kidd blood group system are commonly identified in the Blood Bank, autoantibodies against these antigens are rare and can be associated with hemolysis. We present a case of a pregnant woman identified with anautoanti-Jka.
Study
Design/Methods: Type and screen via gel methodology, direct antiglobulin test (DAT) via tube testing, and antibody identification using untreated and ficin-treated cells were performed at a tertiary care hospital. Elution testing was performed via gel indirect antiglobulin testing. Genomic DNA was isolated from a peripheral blood sample. Sanger sequencing of JK coding exons 3 to 10 and flanking intron regions was performed.
Results/Findings: The patient is a 35-year-old, G2P1001, with a history of asthma who presented for routine prenatal screening. Her prior pregnancy was uncomplicated. The patient is A positive and had a prior positive antibody screen in 2021, at which time no blood group specificity could be determined. A type and screen obtained early in the current pregnancy identified a new anti-Jka (identified on a sample sent to an outside laboratory and a sample sent to our Blood Bank). Serological phenotyping identified the patient as Jk(a+b‒). The DAT and auto-control were positive, and eluate was reactive with all cells with no apparent specificity. Antibody titer was < 1. Sanger sequencing did not detect any variants, and the patient’s inferred genotype was JK*A/A with predicted phenotype Jk(a+b‒), consistent with serology. By sequence results, she is not at risk of producing an alloanti-Jka. Therefore, the patient’s current antibody reactivity reflected an autoanti-Jka. Jka-negative RBCs were added to the patient’s blood requirements due to clinical significance of the autoantibody and her pregnancy status, and ability to obtain crossmatch compatible units. The patient delivered a baby girl at 40 weeks’ gestation via normal spontaneous vaginal delivery with no complications. Baby is O positive and DAT on a cord blood sample was negative. Conclusions: Autoanti-Jka is rarely identified, prompting the importance of phenotypic and genotypic analysis in evaluating these cases. Differentiating between an allo- versus an auto-antibody when the patient is positive for the respective antigen can be difficult. Genotyping then is useful to predict if the patient has an altered antigen and is at risk for an alloantibody. Here, the patient having conventional JK*A alleles supports an autoanti-Jka. While many autoantibodies are generally considered benign, autoanti-Jka has been associated with hemolysis and clinical management can include antigen negative RBCs and antibody titration particularly during pregnancy.
