# Hemolytic Transfusion Reaction Due to Anti-A1 Antibody During Pregnancy: Case Report

## TL;DR

A pregnant woman with sickle cell disease had a severe blood transfusion reaction due to anti-A1 antibodies, highlighting the rare but serious risks in high-risk patients.

## Contribution

This case report highlights the rare clinical significance of anti-A1 antibodies causing delayed hemolytic transfusion reactions in sickle cell disease patients.

## Key findings

- A pregnant woman with sickle cell disease experienced a severe delayed hemolytic transfusion reaction due to anti-A1 antibodies.
- Anti-A1 antibodies were confirmed post-transfusion, and the patient was identified as a non-A1 subtype.
- The case underscores the importance of vigilance in transfusion management for high-risk populations like those with sickle cell disease.

## Abstract

The ABO blood group is the most clinically relevant system in transfusion medicine. Approximately 20% of individuals with blood group A of European descent belong to a weak A subgroup, most commonly A2, which may produce anti-A1 antibodies. These antibodies are usually cold-reactive IgM and rarely cause hemolysis, but can occasionally be clinically significant when reactive at 37°C. We describe a pregnant woman with sickle cell disease (HbS/β0 thalassemia) and prior hyperhemolysis syndrome who developed a severe delayed hemolytic transfusion reaction (DHTR) after transfusion of A1 red blood cells (RBCs). Anti-A1 was identified posttransfusion, confirming her as a non-A1 subtype. Notably, she also experienced hemolysis following group O red cell transfusion, consistent with hyperhemolysis. This case highlights the rare but serious potential of anti-A1 to cause DHTR, particularly in high-risk populations, and underscores the importance of increased vigilance when managing transfusion in sickle cell disease.