[Clinical and genetic analysis of an individual with Lan-negative rare blood group due to variant of ABCB6 gene].

Objective: To investigate a case of antibodies against high-frequency erythrocyte antigens and elucidate the genetic mechanism underlying the blood group.

Methods: A Lan-negative patient referred to the Zhejiang Blood Center by Quzhou Hospital of Traditional Chinese Medicine in August 2016 was selected as the study subject. A retrospective study was conducted to collect the proband's clinical data. The proband's erythrocyte antigens and unexpected serum antibodies were identified using tube saline and microcolumn agglutination anti-human globulin methods. Antibody specificity was determined by treating erythrocytes with 7 enzymes and 2 chemical reducing agents. Genomic DNA was extracted from the proband's blood sample for whole genome sequencing (WGS) and erythrocyte blood group gene analysis, with validation by Sanger sequencing. Multiple bioinformatics tools were used to analyze the pathogenicity of the variant. The rare blood group and unexpected antibody specificity were comprehensively determined based on the results of serological and genetic testing. This study has been approved by the Zhejiang Provincial Blood Center Medical Ethics Committee(Ethics No.20190201).

Results: The proband was a 91-year-old Han Chinese male with prostatitis, cystitis, and malnutrition in conjunct with emaciation. He had a history of multiple erythrocyte transfusions without observable adverse reactions. Prior to the most recent transfusion, major crossmatch agglutination was observed, which prompted antibody identification. Antibodies against high-frequency antigens were detected in the proband's serum, with enzyme and reducing agent treatments ruling out antibody specificities associated with 17 blood group systems, e.g., MNS, LU, KEL. WGS analysis identified 4 525 SNPs and 1 046 INDEL variants among erythrocyte blood group genes. Further screening revealed that the proband had a rare blood group due to a homozygous rs755723161 variant. This variant in the ABCB6 gene (c.459delC) has led to a frameshifting mutation (p.Trp154GlyfsTer96), resulting in the Lan-negative rare blood group with a high-frequency antigen deficiency and the production of IgG anti-Lan antibodies in the serum.

Conclusion: This study has identified anti-Lan alloantibodies in a Lan-negative patient and, for the first time, elucidated the ABCB6 gene variant underlying the Lan-negative rare blood group in the Chinese population.