A novel homozygous KEL variant causing K ₀ phenotype in a Chinese woman and therapeutic plasma exchange for anti‐Ku removal in preoperative management

Background The Kell null (K 0 ) is a rare phenotype characterized by the absence of all Kell blood group antigens. Individuals with K 0 are often identified after developing anti‐Ku, an antibody associated with hemolytic transfusion reactions (HTR) and hemolytic disease of the fetus and newborn (HDFN). Transfusion management in this population is particularly challenging as compatible blood is difficult to find. It is crucial to adopt safe and reliable treatments for preoperative blood management. Study Design and Methods We describe a K 0 woman with potent Ku alloantibody preparing for surgery. Kell antigen typing and titers of anti‐Ku were detected by standard serologic techniques. Polymerase chain reaction (PCR) and DNA sequencing of the KEL coding region were performed on her genomic DNA. Therapeutic plasma exchange (TPE) was initiated for five sessions to reduce the high anti‐Ku titers before surgery. Results The red blood cells (RBCs) phenotype of the Kell blood group was identified as K– k–; Kp(a– b–). DNA sequence analysis revealed the patient was homozygous for a nucleotide deletion, NM_000420.3:c.855delT (p.L286*) in exon 8 of the KEL gene. After TPE, the anti‐Ku titers decreased from 1:1600 to 1:400. A rebound phenomenon was noted during the procedures. Discussion We identified a novel homozygous KEL variant causing K 0 phenotype in a Chinese woman with Ku alloimmunization. TPE proved to be effective for decreasing anti‐Ku titers. However, the rebound of antibodies should be considered when using TPE to decrease the antibody titers. This report demonstrates a new attempt in preoperative transfusion management for patients with rare alloantibodies.