Stanford University School of Medicine, Department of Pathology Mountain View, California, United States
Background/Case Studies: Acute hemolytic transfusion reactions (AHTR) occur in 1:76,000 RBC transfusions. Occasionally, they are caused by non-ABO incompatible transfusions. The Vel blood group system consists of one antigen dependent on SMIM1 expression, which encodes a 78 amino acid single-pass membrane protein. It is a high-frequency antigen present in 99.98% of the population. We present a case of a pregnant woman, G10P6027, who presented to our hospital for the first time at 25-weeks gestation for vaginal bleeding. She was found to have placenta previa and accreta spectrum and required emergent Cesarean delivery.
Study
Design/Methods: Serologic testing was performed and patient records were reviewed.
Results/Findings: The patient typed as A-positive with a positive antibody screen. Antibody identification showed a pan-agglutinin with 2+ to 3+ reactivity with PEG at AHG phase and a negative auto-control. Ficin and DTT treatment of reagent red blood cells (RBCs) did not change reactivity. A cold panel revealed cold agglutinins with some auto-reactivity. Underlying RBC alloantibodies could not be ruled out in time for surgery and emergency release RBCs that were phenotypically matched for all major antigens were issued while the serologic workup continued.
The patient received 6 units of RBCs for intraoperative bleeding. She developed dark urine, rash, and evidence of disseminated intravascular coagulation (DIC). A transfusion reaction work-up revealed visual evidence of hemolysis and a positive, C3-only DAT. Labs showed hyperkalemia, hemoglobin of 3.6 g/dL, and acute kidney injury.
Through the use of rare reagent cells and antisera, the patient was eventually found to have an anti-Vel antibody and later genotyped as Vel-negative. Through the American Rare Donor Program, a search for Vel-negative blood yielded 16 RBCs. We received the first unit within 24 hours of outreach. After a 2-week ICU stay, transfusion of 9 Vel-negative RBCs, and dialysis, she was discharged. Notably, her baby had no evidence of HDFN. Conclusions: This patient represents a rare Vel-negative individual with allo-immunization. Alloanti-Vel is usually a mixture of IgM and IgG and can readily activate complement, which can cause severe AHTRs and, less commonly, HDFN.
Identification of anti-Vel antibodies can be difficult due to their rarity, especially in emergency settings. Not only are Vel-negative RBCs and antisera for testing difficult to obtain, anti-Vel can mimic benign cold-reactive IgM antibodies. In our case, a nearby outside laboratory had previously identified her antibody during routine prenatal testing, although results were not available to us at the time of surgery. This case highlights the need for increased transparency and improved patient education of transfusion-pertinent information by blood banks & reference laboratories.
Importance of research: We present a case of a severe acute hemolytic transfusion reaction (AHTR) due to anti-Vel antibodies in a pregnant woman undergoing emergent Cesarean section. This case highlights one of the rare, non-ABO IgM antibodies causing an AHTR, with significant volume of incompatible pRBC units (6) transfused, as well as the testing difficulties in an emergency setting and the need for transfusion-related data transparency and sharing.
